Merge branch 'youngyangyang04:master' into master

problems/0001.两数之和.md

@@ -317,6 +317,20 @@ public class Solution {
 }
 ```
 
+Dart:
+```dart
+List<int> twoSum(List<int> nums, int target) {  
+    var tmp = [];
+    for (var i = 0; i < nums.length; i++) {
+        var rest = target - nums[i];
+        if(tmp.contains(rest)){
+            return [tmp.indexOf(rest), i];
+        }
+        tmp.add(nums[i]);
+    }
+    return [0 , 0];
+}
+```
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0015.三数之和.md

@@ -554,6 +554,71 @@ func threeSum(_ nums: [Int]) -> [[Int]] {
 }
 ```
 
+Rust:
+```Rust
+// 哈希解法
+use std::collections::HashSet;
+impl Solution {
+    pub fn three_sum(nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut result: Vec<Vec<i32>> = Vec::new();
+        let mut nums = nums;
+        nums.sort();
+        let len = nums.len();
+        for i in 0..len {
+            if nums[i] > 0 { break; }
+            if i > 0 && nums[i] == nums[i - 1] { continue; }
+            let mut set = HashSet::new();
+            for j in (i + 1)..len {
+                if j > i + 2 && nums[j] == nums[j - 1] && nums[j] == nums[j - 2] { continue; }
+                let c = 0 - (nums[i] + nums[j]);
+                if set.contains(&c) {
+                    result.push(vec![nums[i], nums[j], c]);
+                    set.remove(&c);
+                } else { set.insert(nums[j]); }
+            }
+        }
+        result
+    }
+}
+```
+
+```Rust
+// 双指针法
+use std::collections::HashSet;
+impl Solution {
+    pub fn three_sum(nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut result: Vec<Vec<i32>> = Vec::new();
+        let mut nums = nums;
+        nums.sort();
+        let len = nums.len();
+        for i in 0..len {
+            if nums[i] > 0 { return result; }
+            if i > 0 && nums[i] == nums[i - 1] { continue; }
+            let (mut left, mut right) = (i + 1, len - 1);
+            while left < right {
+                if nums[i] + nums[left] + nums[right] > 0 {
+                    right -= 1;
+                    // 去重
+                    while left < right && nums[right] == nums[right + 1] { right -= 1; }
+                } else if nums[i] + nums[left] + nums[right] < 0 {
+                    left += 1;
+                    // 去重
+                    while left < right && nums[left] == nums[left - 1] { left += 1; }
+                } else {
+                    result.push(vec![nums[i], nums[left], nums[right]]);
+                    // 去重
+                    right -= 1;
+                    left += 1;
+                    while left < right && nums[right] == nums[right + 1] { right -= 1; }
+                    while left < right && nums[left] == nums[left - 1] { left += 1; }
+                }
+            }
+        }
+        result
+    }
+}
+```
+
 C:
 ```C
 //qsort辅助cmp函数

problems/0018.四数之和.md

@@ -140,6 +140,11 @@ class Solution {
        
         for (int i = 0; i < nums.length; i++) {
 
+            // nums[i] > target 直接返回, 剪枝操作
+            if (nums[i] > 0 && nums[i] > target) {
+                return result;
+            }
+
             if (i > 0 && nums[i - 1] == nums[i]) {
                 continue;
             }
@@ -522,6 +527,51 @@ public class Solution
     }
 }
 ```
+
+Rust:
+```Rust
+impl Solution {
+    pub fn four_sum(nums: Vec<i32>, target: i32) -> Vec<Vec<i32>> {
+        let mut result: Vec<Vec<i32>> = Vec::new();
+        let mut nums = nums;
+        nums.sort();
+        let len = nums.len();
+        for k in 0..len {
+            // 剪枝
+            if nums[k] > target && (nums[k] > 0 || target > 0) { break; }
+            // 去重
+            if k > 0 && nums[k] == nums[k - 1] { continue; }
+            for i in (k + 1)..len {
+                // 剪枝
+                if nums[k] + nums[i] > target && (nums[k] + nums[i] >= 0 || target >= 0) { break; }
+                // 去重
+                if i > k + 1 && nums[i] == nums[i - 1] { continue; }
+                let (mut left, mut right) = (i + 1, len - 1);
+                while left < right {
+                    if nums[k] + nums[i] > target - (nums[left] + nums[right]) {
+                        right -= 1;
+                        // 去重
+                        while left < right && nums[right] == nums[right + 1] { right -= 1; }
+                    } else if nums[k] + nums[i] < target - (nums[left] + nums[right]) {
+                        left += 1;
+                        // 去重
+                        while left < right && nums[left] == nums[left - 1] { left += 1; }
+                    } else {
+                        result.push(vec![nums[k], nums[i], nums[left], nums[right]]);
+                        // 去重
+                        while left < right && nums[right] == nums[right - 1] { right -= 1; }
+                        while left < right && nums[left] == nums[left + 1] { left += 1; }
+                        left += 1;
+                        right -= 1;
+                    }
+                }
+            }
+        }
+        result
+    }
+}
+```
+
 Scala:
 ```scala
 object Solution {

problems/0046.全排列.md

@@ -456,6 +456,36 @@ func permute(_ nums: [Int]) -> [[Int]] {
 }
 ```
 
+### Scala
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def permute(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+
+    def backtracking(used: Array[Boolean]): Unit = {
+      if (path.size == nums.size) {
+        // 如果path的长度和nums相等，那么可以添加到结果集
+        result.append(path.toList)
+        return
+      }
+      // 添加循环守卫，只有当当前数字没有用过的情况下才进入回溯
+      for (i <- nums.indices if used(i) == false) {
+        used(i) = true
+        path.append(nums(i))
+        backtracking(used) // 回溯
+        path.remove(path.size - 1)
+        used(i) = false
+      }
+    }
+
+    backtracking(new Array[Boolean](nums.size)) // 调用方法
+    result.toList // 最终返回结果集的List形式
+  }
+}
+```
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0047.全排列II.md

@@ -422,5 +422,43 @@ int** permuteUnique(int* nums, int numsSize, int* returnSize, int** returnColumn
 }
 ```
 
+### Scala
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def permuteUnique(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+    var num = nums.sorted // 首先对数据进行排序
+
+    def backtracking(used: Array[Boolean]): Unit = {
+      if (path.size == num.size) {
+        // 如果path的size等于num了，那么可以添加到结果集
+        result.append(path.toList)
+        return
+      }
+      // 循环守卫，当前元素没被使用过就进入循环体
+      for (i <- num.indices if used(i) == false) {
+        // 当前索引为0，不存在和前一个数字相等可以进入回溯
+        // 当前索引值和上一个索引不相等，可以回溯
+        // 前一个索引对应的值没有被选，可以回溯
+        // 因为Scala没有continue，只能将逻辑反过来写 
+        if (i == 0 || (i > 0 && num(i) != num(i - 1)) || used(i-1) == false) {
+          used(i) = true
+          path.append(num(i))
+          backtracking(used)
+          path.remove(path.size - 1)
+          used(i) = false
+        }
+      }
+    }
+
+    backtracking(new Array[Boolean](nums.length))
+    result.toList
+  }
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0051.N皇后.md

@@ -455,7 +455,7 @@ var solveNQueens = function(n) {
 };
 ```
 
-## TypeScript
+### TypeScript
 
 ```typescript
 function solveNQueens(n: number): string[][] {
@@ -683,5 +683,77 @@ char *** solveNQueens(int n, int* returnSize, int** returnColumnSizes){
 }
 ```
 
+### Scala
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def solveNQueens(n: Int): List[List[String]] = {
+    var result = mutable.ListBuffer[List[String]]()
+
+    def judge(x: Int, y: Int, maze: Array[Array[Boolean]]): Boolean = {
+      // 正上方
+      var xx = x
+      while (xx >= 0) {
+        if (maze(xx)(y)) return false
+        xx -= 1
+      }
+      // 左边
+      var yy = y
+      while (yy >= 0) {
+        if (maze(x)(yy)) return false
+        yy -= 1
+      }
+      // 左上方
+      xx = x
+      yy = y
+      while (xx >= 0 && yy >= 0) {
+        if (maze(xx)(yy)) return false
+        xx -= 1
+        yy -= 1
+      }
+      xx = x
+      yy = y
+      // 右上方
+      while (xx >= 0 && yy < n) {
+        if (maze(xx)(yy)) return false
+        xx -= 1
+        yy += 1
+      }
+      true
+    }
+
+    def backtracking(row: Int, maze: Array[Array[Boolean]]): Unit = {
+      if (row == n) {
+        // 将结果转换为题目所需要的形式
+        var path = mutable.ListBuffer[String]()
+        for (x <- maze) {
+          var tmp = mutable.ListBuffer[String]()
+          for (y <- x) {
+            if (y == true) tmp.append("Q")
+            else tmp.append(".")
+          }
+          path.append(tmp.mkString)
+        }
+        result.append(path.toList)
+        return
+      }
+
+      for (j <- 0 until n) {
+        // 判断这个位置是否可以放置皇后
+        if (judge(row, j, maze)) {
+          maze(row)(j) = true
+          backtracking(row + 1, maze)
+          maze(row)(j) = false
+        }
+      }
+    }
+
+    backtracking(0, Array.ofDim[Boolean](n, n))
+    result.toList
+  }
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0056.合并区间.md

@@ -136,24 +136,38 @@ public:
 
 ### Java 
 ```java
+
+/**
+时间复杂度 ： O(NlogN) 排序需要O(NlogN)
+空间复杂度 ： O(logN)  java 的内置排序是快速排序 需要 O(logN)空间
+
+*/
 class Solution {
     public int[][] merge(int[][] intervals) {
         List<int[]> res = new LinkedList<>();
-        Arrays.sort(intervals, (o1, o2) -> Integer.compare(o1[0], o2[0]));
+        //按照左边界排序
-
+        Arrays.sort(intervals, (x, y) -> Integer.compare(x[0], y[0]));
+        //initial start 是最小左边界
         int start = intervals[0][0];
+        int rightmostRightBound = intervals[0][1];
         for (int i = 1; i < intervals.length; i++) {
-            if (intervals[i][0] > intervals[i - 1][1]) {
+            //如果左边界大于最大右边界
-                res.add(new int[]{start, intervals[i - 1][1]});
+            if (intervals[i][0] > rightmostRightBound) {
+                //加入区间 并且更新start
+                res.add(new int[]{start, rightmostRightBound});
                 start = intervals[i][0];
+                rightmostRightBound = intervals[i][1];
             } else {
-                intervals[i][1] = Math.max(intervals[i][1], intervals[i - 1][1]);
+                //更新最大右边界
+                rightmostRightBound = Math.max(rightmostRightBound, intervals[i][1]);
             }
         }
-        res.add(new int[]{start, intervals[intervals.length - 1][1]});
+        res.add(new int[]{start, rightmostRightBound});
         return res.toArray(new int[res.size()][]);
     }
 }
+
+}
 ```
 ```java
 // 版本2

problems/0078.子集.md

@@ -373,6 +373,60 @@ func subsets(_ nums: [Int]) -> [[Int]] {
 }
 ```
 
+## Scala
+
+思路一: 使用本题解思路
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsets(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+
+    def backtracking(startIndex: Int): Unit = {
+      result.append(path.toList) // 存放结果
+      if (startIndex >= nums.size) {
+        return
+      }
+      for (i <- startIndex until nums.size) {
+        path.append(nums(i)) // 添加元素
+        backtracking(i + 1)
+        path.remove(path.size - 1) // 删除
+      }
+    }
+
+    backtracking(0)
+    result.toList
+  }
+}
+```
+
+思路二: 将原问题转换为二叉树，针对每一个元素都有**选或不选**两种选择，直到遍历到最后，所有的叶子节点即为本题的答案：
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsets(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+
+    def backtracking(path: mutable.ListBuffer[Int], startIndex: Int): Unit = {
+      if (startIndex == nums.length) {
+        result.append(path.toList)
+        return
+      }
+      path.append(nums(startIndex))
+      backtracking(path, startIndex + 1)  // 选择元素
+      path.remove(path.size - 1)
+      backtracking(path, startIndex + 1)  // 不选择元素
+    }
+
+    backtracking(mutable.ListBuffer[Int](), 0)
+    result.toList
+  }
+}
+```
+
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0090.子集II.md

@@ -434,6 +434,63 @@ func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
 }
 ```
 
+### Scala
+
+不使用userd数组:
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsetsWithDup(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+    var num = nums.sorted // 排序
+
+    def backtracking(startIndex: Int): Unit = {
+      result.append(path.toList)
+      if (startIndex >= num.size){
+        return
+      }
+      for (i <- startIndex until num.size) {
+        // 同一树层重复的元素不进入回溯
+        if (!(i > startIndex && num(i) == num(i - 1))) {
+          path.append(num(i))
+          backtracking(i + 1)
+          path.remove(path.size - 1)
+        }
+      }
+    }
+
+    backtracking(0)
+    result.toList
+  }
+}
+```
+
+使用Set去重:
+```scala
+object Solution {
+  import scala.collection.mutable
+  def subsetsWithDup(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.Set[List[Int]]()
+    var num = nums.sorted
+    def backtracking(path: mutable.ListBuffer[Int], startIndex: Int): Unit = {
+      if (startIndex == num.length) {
+        result.add(path.toList)
+        return
+      }
+      path.append(num(startIndex))
+      backtracking(path, startIndex + 1)  // 选择
+      path.remove(path.size - 1)
+      backtracking(path, startIndex + 1)  // 不选择
+    }
+
+    backtracking(mutable.ListBuffer[Int](), 0)
+
+    result.toList
+  }
+}
+```
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0102.二叉树的层序遍历.md

@@ -2629,21 +2629,21 @@ JavaScript：
 var minDepth = function(root) {
     if (root === null) return 0;
     let queue = [root];
-    let deepth = 0;
+    let depth = 0;
     while (queue.length) {
         let n = queue.length;
-        deepth++;
+        depth++;
         for (let i=0; i<n; i++) {
             let node = queue.shift();
-            // 如果左右节点都是null，则该节点深度最小
+            // 如果左右节点都是null(在遇见的第一个leaf节点上)，则该节点深度最小
             if (node.left === null && node.right === null) {
-                return deepth;
+                return depth;
             }
             node.left && queue.push(node.left);;
-            node.right && queue.push (node.right);
+            node.right && queue.push(node.right);
         }
     }
-    return deepth;
+    return depth;
 };
 ```
 

problems/0104.二叉树的最大深度.md

@@ -294,14 +294,13 @@ class solution {
     /**
      * 递归法
      */
-    public int maxdepth(treenode root) {
+    public int maxDepth(TreeNode root) {
         if (root == null) {
             return 0;
         }
-        int leftdepth = maxdepth(root.left);
+        int leftDepth = maxDepth(root.left);
-        int rightdepth = maxdepth(root.right);
+        int rightDepth = maxDepth(root.right);
-        return math.max(leftdepth, rightdepth) + 1;
+        return Math.max(leftDepth, rightDepth) + 1;
-
     }
 }
 ```
@@ -311,23 +310,23 @@ class solution {
     /**
      * 迭代法，使用层序遍历
      */
-    public int maxdepth(treenode root) {
+    public int maxDepth(TreeNode root) {
         if(root == null) {
             return 0;
         }
-        deque<treenode> deque = new linkedlist<>();
+        Deque<TreeNode> deque = new LinkedList<>();
         deque.offer(root);
         int depth = 0;
-        while (!deque.isempty()) {
+        while (!deque.isEmpty()) {
             int size = deque.size();
             depth++;
             for (int i = 0; i < size; i++) {
-                treenode poll = deque.poll();
+                TreeNode node = deque.poll();
-                if (poll.left != null) {
+                if (node.left != null) {
-                    deque.offer(poll.left);
+                    deque.offer(node.left);
                 }
-                if (poll.right != null) {
+                if (node.right != null) {
-                    deque.offer(poll.right);
+                    deque.offer(node.right);
                 }
             }
         }

problems/0129.求根到叶子节点数字之和.md

@@ -3,6 +3,9 @@
   <img src="https://code-thinking-1253855093.file.myqcloud.com/pics/20210924105952.png" width="1000"/>
 </a>
 <p align="center"><strong><a href="https://mp.weixin.qq.com/s/tqCxrMEU-ajQumL1i8im9A">参与本项目</a>，贡献其他语言版本的代码，拥抱开源，让更多学习算法的小伙伴们收益！</strong></p>
+
+
+
 # 129. 求根节点到叶节点数字之和
 
 [力扣题目链接](https://leetcode.cn/problems/sum-root-to-leaf-numbers/)
@@ -245,6 +248,29 @@ class Solution:
 ```
 Go：
 
+```go
+func sumNumbers(root *TreeNode) int {
+	sum = 0
+	travel(root, root.Val)
+	return sum
+}
+
+func travel(root *TreeNode, tmpSum int) {
+	if root.Left == nil && root.Right == nil {
+		sum += tmpSum
+	} else {
+		if root.Left != nil {
+			travel(root.Left, tmpSum*10+root.Left.Val)
+		}
+		if root.Right != nil {
+			travel(root.Right, tmpSum*10+root.Right.Val)
+		}
+	}
+}
+```
+
+
+
 JavaScript：
 ```javascript
 var sumNumbers = function(root) {

problems/0132.分割回文串II.md

@@ -206,6 +206,55 @@ public:
 ## Java
 
 ```java
+class Solution {
+
+    public int minCut(String s) {
+        if(null == s || "".equals(s)){
+            return 0;
+        }
+        int len = s.length();
+        // 1.
+        // 记录子串[i..j]是否是回文串
+        boolean[][] isPalindromic = new boolean[len][len];
+        // 从下到上，从左到右
+        for(int i = len - 1; i >= 0; i--){
+            for(int j = i; j < len; j++){
+                if(s.charAt(i) == s.charAt(j)){
+                    if(j - i <= 1){
+                        isPalindromic[i][j] = true;
+                    } else{
+                        isPalindromic[i][j] = isPalindromic[i + 1][j - 1];
+                    }
+                } else{
+                    isPalindromic[i][j] = false;
+                }
+            }
+        }
+
+        // 2.
+        // dp[i] 表示[0..i]的最小分割次数
+        int[] dp = new int[len];
+        for(int i = 0; i < len; i++){
+            //初始考虑最坏的情况。 1个字符分割0次， len个字符分割 len - 1次
+            dp[i] = i;
+        }
+
+        for(int i = 1; i < len; i++){
+            if(isPalindromic[0][i]){
+                // s[0..i]是回文了，那 dp[i] = 0, 一次也不用分割
+                dp[i] = 0;
+                continue;
+            }
+            for(int j = 0; j < i; j++){
+                // 按文中的思路，不清楚就拿 "ababa" 为例，先写出 isPalindromic 数组，再进行求解
+                if(isPalindromic[j + 1][i]){
+                    dp[i] = Math.min(dp[i], dp[j] + 1);
+                }
+            }
+        }
+        return dp[len - 1];
+    }
+}
 ```
 
 ## Python
@@ -240,6 +289,7 @@ class Solution:
 ## Go
 
 ```go
+
 ```
 
 ## JavaScript

problems/0202.快乐数.md

@@ -315,6 +315,36 @@ class Solution {
 }
 ```
 
+Rust:
+```Rust
+use std::collections::HashSet;
+impl Solution {
+    pub fn get_sum(mut n: i32) -> i32 {
+        let mut sum = 0;
+        while n > 0 {
+            sum += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        sum
+    }
+
+    pub fn is_happy(n: i32) -> bool {
+        let mut n = n;
+        let mut set = HashSet::new();
+        loop {
+            let sum = Self::get_sum(n);
+            if sum == 1 {
+                return true;
+            }
+            if set.contains(&sum) {
+                return false;
+            } else { set.insert(sum); }
+            n = sum;
+        }
+    }
+}
+```
+
 C:
 ```C
 typedef struct HashNodeTag {

problems/0205.同构字符串.md

@@ -156,6 +156,28 @@ var isIsomorphic = function(s, t) {
 };
 ```
 
+## TypeScript
+
+```typescript
+function isIsomorphic(s: string, t: string): boolean {
+    const helperMap1: Map<string, string> = new Map();
+    const helperMap2: Map<string, string> = new Map();
+    for (let i = 0, length = s.length; i < length; i++) {
+        let temp1: string | undefined = helperMap1.get(s[i]);
+        let temp2: string | undefined = helperMap2.get(t[i]);
+        if (temp1 === undefined && temp2 === undefined) {
+            helperMap1.set(s[i], t[i]);
+            helperMap2.set(t[i], s[i]);
+        } else if (temp1 !== t[i] || temp2 !== s[i]) {
+            return false;
+        }
+    }
+    return true;
+};
+```
+
+
+
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0226.翻转二叉树.md

@@ -470,25 +470,14 @@ func invertTree(root *TreeNode) *TreeNode {
 使用递归版本的前序遍历
 ```javascript
 var invertTree = function(root) {
-    //1. 首先使用递归版本的前序遍历实现二叉树翻转
+    // 终止条件
-    //交换节点函数
+    if (!root) {
-    const inverNode=function(left,right){
+        return null;
-        let temp=left;
-        left=right;
-        right=temp;
-        //需要重新给root赋值一下
-        root.left=left;
-        root.right=right;
     }
-    //确定递归函数的参数和返回值inverTree=function(root)
+    // 交换左右节点
-    //确定终止条件
+    const rightNode = root.right;
-    if(root===null){
+    root.right = invertTree(root.left);
-        return root;
+    root.left = invertTree(rightNode);
-    }
-    //确定节点处理逻辑 交换
-    inverNode(root.left,root.right);
-    invertTree(root.left);
-    invertTree(root.right);
     return root;
 };
 ```

problems/0347.前K个高频元素.md

@@ -141,13 +141,10 @@ class Solution {
         }
 
         Set<Map.Entry<Integer, Integer>> entries = map.entrySet();
-        // 根据map的value值正序排，相当于一个小顶堆
+        // 根据map的value值，构建于一个大顶堆（o1 - o2: 小顶堆， o2 - o1 : 大顶堆）
-        PriorityQueue<Map.Entry<Integer, Integer>> queue = new PriorityQueue<>((o1, o2) -> o1.getValue() - o2.getValue());
+        PriorityQueue<Map.Entry<Integer, Integer>> queue = new PriorityQueue<>((o1, o2) -> o2.getValue() - o1.getValue());
         for (Map.Entry<Integer, Integer> entry : entries) {
             queue.offer(entry);
-            if (queue.size() > k) {
-                queue.poll();
-            }
         }
         for (int i = k - 1; i >= 0; i--) {
             result[i] = queue.poll().getKey();

problems/0450.删除二叉搜索树中的节点.md

@@ -456,31 +456,42 @@ func deleteNode(root *TreeNode, key int) *TreeNode {
  * @param {number} key
  * @return {TreeNode}
  */
-var deleteNode = function (root, key) {
+var deleteNode = function(root, key) {
-    if (root === null)
+    if (!root) return null;
-        return root;
+    if (key > root.val) {
-    if (root.val === key) {
-        if (!root.left)
-            return root.right;
-        else if (!root.right)
-            return root.left;
-        else {
-            let cur = root.right;
-            while (cur.left) {
-                cur = cur.left;
-            }
-            cur.left = root.left;
-            root = root.right;
-            delete root;
-            return root;
-        }
-    }
-    if (root.val > key)
-        root.left = deleteNode(root.left, key);
-    if (root.val < key)
         root.right = deleteNode(root.right, key);
-    return root;
+        return root;
+    } else if (key < root.val) {
+        root.left = deleteNode(root.left, key);
+        return root;
+    } else {
+        // 场景1: 该节点是叶节点
+        if (!root.left && !root.right) {
+            return null
+        }
+        // 场景2: 有一个孩子节点不存在
+        if (root.left && !root.right) {
+            return root.left;
+        } else if (root.right && !root.left) {
+            return root.right;
+        }
+        // 场景3: 左右节点都存在
+        const rightNode = root.right;
+        // 获取最小值节点
+        const minNode = getMinNode(rightNode);
+        // 将待删除节点的值替换为最小值节点值
+        root.val = minNode.val;
+        // 删除最小值节点
+        root.right = deleteNode(root.right, minNode.val);
+        return root;
+    }
 };
+function getMinNode(root) {
+    while (root.left) {
+        root = root.left;
+    }
+    return root;
+}
 ```
 
 迭代

problems/0452.用最少数量的箭引爆气球.md

@@ -136,17 +136,28 @@ public:
 
 ### Java 
 ```java
+/**
+时间复杂度 : O(NlogN)  排序需要 O(NlogN) 的复杂度
+
+空间复杂度 : O(logN) java所使用的内置函数用的是快速排序需要 logN 的空间
+*/
 class Solution {
     public int findMinArrowShots(int[][] points) {
         if (points.length == 0) return 0;
-        Arrays.sort(points, (o1, o2) -> Integer.compare(o1[0], o2[0]));
+        //用x[0] - y[0] 会大于2147483647 造成整型溢出
-
+        Arrays.sort(points, (x, y) -> Integer.compare(x[0], y[0]));
+        //count = 1 因为最少需要一个箭来射击第一个气球
         int count = 1;
-        for (int i = 1; i < points.length; i++) {
+        //重叠气球的最小右边界
-            if (points[i][0] > points[i - 1][1]) {
+        int leftmostRightBound  = points[0][1];
+        //如果下一个气球的左边界大于最小右边界
+            if (points[i][0] > leftmostRightBound ) {
+                //增加一次射击
                 count++;
+                leftmostRightBound  = points[i][1];
+                //不然就更新最小右边界
             } else {
-                points[i][1] = Math.min(points[i][1],points[i - 1][1]);
+                leftmostRightBound  = Math.min(leftmostRightBound , points[i][1]);
             }
         }
         return count;

problems/0491.递增子序列.md

@@ -522,5 +522,39 @@ func findSubsequences(_ nums: [Int]) -> [[Int]] {
 ```
 
 
+## Scala
+
+```scala
+object Solution {
+  import scala.collection.mutable
+  def findSubsequences(nums: Array[Int]): List[List[Int]] = {
+    var result = mutable.ListBuffer[List[Int]]()
+    var path = mutable.ListBuffer[Int]()
+
+    def backtracking(startIndex: Int): Unit = {
+      // 集合元素大于1，添加到结果集
+      if (path.size > 1) {
+        result.append(path.toList)
+      }
+
+      var used = new Array[Boolean](201)
+      // 使用循环守卫，当前层没有用过的元素才有资格进入回溯
+      for (i <- startIndex until nums.size if !used(nums(i) + 100)) {
+        // 如果path没元素或 当前循环的元素比path的最后一个元素大，则可以进入回溯
+        if (path.size == 0 || (!path.isEmpty && nums(i) >= path(path.size - 1))) {
+          used(nums(i) + 100) = true
+          path.append(nums(i))
+          backtracking(i + 1)
+          path.remove(path.size - 1)
+        }
+      }
+    }
+
+    backtracking(0)
+    result.toList
+  }
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0977.有序数组的平方.md

@@ -106,6 +106,7 @@ class Solution {
         int index = result.length - 1;
         while (left <= right) {
             if (nums[left] * nums[left] > nums[right] * nums[right]) {
+                // 正数的相对位置是不变的， 需要调整的是负数平方后的相对位置
                 result[index--] = nums[left] * nums[left];
                 ++left;
             } else {

problems/1143.最长公共子序列.md

@@ -129,6 +129,9 @@ public:
 Java：
 
 ```java
+/*
+	二维dp数组
+*/
 class Solution {
     public int longestCommonSubsequence(String text1, String text2) {
         int[][] dp = new int[text1.length() + 1][text2.length() + 1]; // 先对dp数组做初始化操作
@@ -146,6 +149,47 @@ class Solution {
         return dp[text1.length()][text2.length()];
     }
 }
+
+
+
+/**
+	一维dp数组
+*/
+class Solution {
+    public int longestCommonSubsequence(String text1, String text2) {
+        int n1 = text1.length();
+        int n2 = text2.length();
+
+        // 多从二维dp数组过程分析  
+        // 关键在于  如果记录  dp[i - 1][j - 1]
+        // 因为 dp[i - 1][j - 1]  <!=>  dp[j - 1]  <=>  dp[i][j - 1]
+        int [] dp = new int[n2 + 1];
+
+        for(int i = 1; i <= n1; i++){
+
+            // 这里pre相当于 dp[i - 1][j - 1]
+            int pre = dp[0];
+            for(int j = 1; j <= n2; j++){
+
+                //用于给pre赋值
+                int cur = dp[j];
+                if(text1.charAt(i - 1) == text2.charAt(j - 1)){
+                    //这里pre相当于dp[i - 1][j - 1]   千万不能用dp[j - 1] !!
+                    dp[j] = pre + 1;
+                } else{
+                    // dp[j]     相当于   dp[i - 1][j]
+                    // dp[j - 1] 相当于   dp[i][j - 1]
+                    dp[j] = Math.max(dp[j], dp[j - 1]);
+                }
+
+                //更新dp[i - 1][j - 1], 为下次使用做准备
+                pre = cur;
+            }
+        }
+
+        return dp[n2];
+    }
+}
 ```
 
 Python：