diff --git a/problems/0017.电话号码的字母组合.md b/problems/0017.电话号码的字母组合.md
index 2b5cb978..e357a33b 100644
--- a/problems/0017.电话号码的字母组合.md
+++ b/problems/0017.电话号码的字母组合.md
@@ -557,6 +557,37 @@ func letterCombinations(_ digits: String) -> [String] {
}
```
+## Scala:
+
+```scala
+object Solution {
+ import scala.collection.mutable
+ def letterCombinations(digits: String): List[String] = {
+ var result = mutable.ListBuffer[String]()
+ if(digits == "") return result.toList // 如果参数为空，返回空结果集的List形式
+ var path = mutable.ListBuffer[Char]()
+ // 数字和字符的映射关系
+ val map = Array[String]("", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz")
+
+ def backtracking(index: Int): Unit = {
+ if (index == digits.size) {
+ result.append(path.mkString) // mkString语法：将数组类型直接转换为字符串
+ return
+ }
+ var digit = digits(index) - '0' // 这里使用toInt会报错！必须 -'0'
+ for (i <- 0 until map(digit).size) {
+ path.append(map(digit)(i))
+ backtracking(index + 1)
+ path = path.take(path.size - 1)
+ }
+ }
+
+ backtracking(0)
+ result.toList
+ }
+}
+```
+
-----------------------
diff --git a/problems/0027.移除元素.md b/problems/0027.移除元素.md
index 03c58b43..9d687cfb 100644
--- a/problems/0027.移除元素.md
+++ b/problems/0027.移除元素.md
@@ -339,7 +339,6 @@ int removeElement(int* nums, int numsSize, int val){
}
```
-
Kotlin:
```kotlin
fun removeElement(nums: IntArray, `val`: Int): Int {
@@ -351,7 +350,6 @@ fun removeElement(nums: IntArray, `val`: Int): Int {
}
```
-
Scala:
```scala
object Solution {
@@ -368,5 +366,20 @@ object Solution {
}
```
+C#:
+```csharp
+public class Solution {
+ public int RemoveElement(int[] nums, int val) {
+ int slow = 0;
+ for (int fast = 0; fast < nums.Length; fast++) {
+ if (val != nums[fast]) {
+ nums[slow++] = nums[fast];
+ }
+ }
+ return slow;
+ }
+}
+```
+
-----------------------
diff --git a/problems/0039.组合总和.md b/problems/0039.组合总和.md
index fef9b676..564d13ea 100644
--- a/problems/0039.组合总和.md
+++ b/problems/0039.组合总和.md
@@ -502,5 +502,35 @@ func combinationSum(_ candidates: [Int], _ target: Int) -> [[Int]] {
}
```
+## Scala
+
+```scala
+object Solution {
+ import scala.collection.mutable
+ def combinationSum(candidates: Array[Int], target: Int): List[List[Int]] = {
+ var result = mutable.ListBuffer[List[Int]]()
+ var path = mutable.ListBuffer[Int]()
+
+ def backtracking(sum: Int, index: Int): Unit = {
+ if (sum == target) {
+ result.append(path.toList) // 如果正好等于target，就添加到结果集
+ return
+ }
+ // 应该是从当前索引开始的，而不是从0
+ // 剪枝优化：添加循环守卫，当sum + c(i) <= target的时候才循环，才可以进入下一次递归
+ for (i <- index until candidates.size if sum + candidates(i) <= target) {
+ path.append(candidates(i))
+ backtracking(sum + candidates(i), i)
+ path = path.take(path.size - 1)
+ }
+ }
+
+ backtracking(0, 0)
+ result.toList
+ }
+}
+```
+
+
-----------------------
diff --git a/problems/0040.组合总和II.md b/problems/0040.组合总和II.md
index ee4371cd..557eb855 100644
--- a/problems/0040.组合总和II.md
+++ b/problems/0040.组合总和II.md
@@ -693,5 +693,37 @@ func combinationSum2(_ candidates: [Int], _ target: Int) -> [[Int]] {
}
```
+
+## Scala
+
+```scala
+object Solution {
+ import scala.collection.mutable
+ def combinationSum2(candidates: Array[Int], target: Int): List[List[Int]] = {
+ var res = mutable.ListBuffer[List[Int]]()
+ var path = mutable.ListBuffer[Int]()
+ var candidate = candidates.sorted
+
+ def backtracking(sum: Int, startIndex: Int): Unit = {
+ if (sum == target) {
+ res.append(path.toList)
+ return
+ }
+
+ for (i <- startIndex until candidate.size if sum + candidate(i) <= target) {
+ if (!(i > startIndex && candidate(i) == candidate(i - 1))) {
+ path.append(candidate(i))
+ backtracking(sum + candidate(i), i + 1)
+ path = path.take(path.size - 1)
+ }
+ }
+ }
+
+ backtracking(0, 0)
+ res.toList
+ }
+}
+```
+
-----------------------
diff --git a/problems/0077.组合.md b/problems/0077.组合.md
index 8d22d018..fc72be15 100644
--- a/problems/0077.组合.md
+++ b/problems/0077.组合.md
@@ -673,5 +673,63 @@ func combine(_ n: Int, _ k: Int) -> [[Int]] {
}
```
+### Scala
+
+暴力:
+```scala
+object Solution {
+ import scala.collection.mutable // 导包
+ def combine(n: Int, k: Int): List[List[Int]] = {
+ var result = mutable.ListBuffer[List[Int]]() // 存放结果集
+ var path = mutable.ListBuffer[Int]() //存放符合条件的结果
+
+ def backtracking(n: Int, k: Int, startIndex: Int): Unit = {
+ if (path.size == k) {
+ // 如果path的size == k就达到题目要求，添加到结果集，并返回
+ result.append(path.toList)
+ return
+ }
+ for (i <- startIndex to n) { // 遍历从startIndex到n
+ path.append(i) // 先把数字添加进去
+ backtracking(n, k, i + 1) // 进行下一步回溯
+ path = path.take(path.size - 1) // 回溯完再删除掉刚刚添加的数字
+ }
+ }
+
+ backtracking(n, k, 1) // 执行回溯
+ result.toList // 最终返回result的List形式，return关键字可以省略
+ }
+}
+```
+
+剪枝:
+
+```scala
+object Solution {
+ import scala.collection.mutable // 导包
+ def combine(n: Int, k: Int): List[List[Int]] = {
+ var result = mutable.ListBuffer[List[Int]]() // 存放结果集
+ var path = mutable.ListBuffer[Int]() //存放符合条件的结果
+
+ def backtracking(n: Int, k: Int, startIndex: Int): Unit = {
+ if (path.size == k) {
+ // 如果path的size == k就达到题目要求，添加到结果集，并返回
+ result.append(path.toList)
+ return
+ }
+ // 剪枝优化
+ for (i <- startIndex to (n - (k - path.size) + 1)) {
+ path.append(i) // 先把数字添加进去
+ backtracking(n, k, i + 1) // 进行下一步回溯
+ path = path.take(path.size - 1) // 回溯完再删除掉刚刚添加的数字
+ }
+ }
+
+ backtracking(n, k, 1) // 执行回溯
+ result.toList // 最终返回result的List形式，return关键字可以省略
+ }
+}
+```
+
-----------------------
diff --git a/problems/0077.组合优化.md b/problems/0077.组合优化.md
index a6767047..8d742566 100644
--- a/problems/0077.组合优化.md
+++ b/problems/0077.组合优化.md
@@ -346,5 +346,34 @@ func combine(_ n: Int, _ k: Int) -> [[Int]] {
}
```
+Scala:
+
+```scala
+object Solution {
+ import scala.collection.mutable // 导包
+ def combine(n: Int, k: Int): List[List[Int]] = {
+ var result = mutable.ListBuffer[List[Int]]() // 存放结果集
+ var path = mutable.ListBuffer[Int]() //存放符合条件的结果
+
+ def backtracking(n: Int, k: Int, startIndex: Int): Unit = {
+ if (path.size == k) {
+ // 如果path的size == k就达到题目要求，添加到结果集，并返回
+ result.append(path.toList)
+ return
+ }
+ // 剪枝优化
+ for (i <- startIndex to (n - (k - path.size) + 1)) {
+ path.append(i) // 先把数字添加进去
+ backtracking(n, k, i + 1) // 进行下一步回溯
+ path = path.take(path.size - 1) // 回溯完再删除掉刚刚添加的数字
+ }
+ }
+
+ backtracking(n, k, 1) // 执行回溯
+ result.toList // 最终返回result的List形式，return关键字可以省略
+ }
+}
+```
+
-----------------------
diff --git a/problems/0216.组合总和III.md b/problems/0216.组合总和III.md
index 0ace0fd5..2c1bf717 100644
--- a/problems/0216.组合总和III.md
+++ b/problems/0216.组合总和III.md
@@ -502,5 +502,35 @@ func combinationSum3(_ count: Int, _ targetSum: Int) -> [[Int]] {
}
```
+## Scala
+
+```scala
+object Solution {
+ import scala.collection.mutable
+ def combinationSum3(k: Int, n: Int): List[List[Int]] = {
+ var result = mutable.ListBuffer[List[Int]]()
+ var path = mutable.ListBuffer[Int]()
+
+ def backtracking(k: Int, n: Int, sum: Int, startIndex: Int): Unit = {
+ if (sum > n) return // 剪枝，如果sum>目标和，就返回
+ if (sum == n && path.size == k) {
+ result.append(path.toList)
+ return
+ }
+ // 剪枝
+ for (i <- startIndex to (9 - (k - path.size) + 1)) {
+ path.append(i)
+ backtracking(k, n, sum + i, i + 1)
+ path = path.take(path.size - 1)
+ }
+ }
+
+ backtracking(k, n, 0, 1) // 调用递归方法
+ result.toList // 最终返回结果集的List形式
+ }
+}
+```
+
+
-----------------------
diff --git a/problems/0239.滑动窗口最大值.md b/problems/0239.滑动窗口最大值.md
index 23e79c80..7ee1fdb1 100644
--- a/problems/0239.滑动窗口最大值.md
+++ b/problems/0239.滑动窗口最大值.md
@@ -654,8 +654,7 @@ object Solution {
// 最终返回res，return关键字可以省略
res
}
-
-}
+ }
class MyQueue {
var queue = ArrayBuffer[Int]()
@@ -678,5 +677,84 @@ class MyQueue {
def peek(): Int = queue.head
}
```
+
+
+PHP:
+```php
+class Solution {
+ /**
+ * @param Integer[] $nums
+ * @param Integer $k
+ * @return Integer[]
+ */
+ function maxSlidingWindow($nums, $k) {
+ $myQueue = new MyQueue();
+ // 先将前k的元素放进队列
+ for ($i = 0; $i < $k; $i++) {
+ $myQueue->push($nums[$i]);
+ }
+
+ $result = [];
+ $result[] = $myQueue->max(); // result 记录前k的元素的最大值
+
+ for ($i = $k; $i < count($nums); $i++) {
+ $myQueue->pop($nums[$i - $k]); // 滑动窗口移除最前面元素
+ $myQueue->push($nums[$i]); // 滑动窗口前加入最后面的元素
+ $result[]= $myQueue->max(); // 记录对应的最大值
+ }
+ return $result;
+ }
+
+}
+
+// 单调对列构建
+class MyQueue{
+ private $queue;
+
+ public function __construct(){
+ $this->queue = new SplQueue(); //底层是双向链表实现。
+ }
+
+ public function pop($v){
+ // 判断当前对列是否为空
+ // 比较当前要弹出的数值是否等于队列出口元素的数值，如果相等则弹出。
+ // bottom 从链表前端查看元素, dequeue 从双向链表的开头移动一个节点
+ if(!$this->queue->isEmpty() && $v == $this->queue->bottom()){
+ $this->queue->dequeue(); //弹出队列
+ }
+ }
+
+ public function push($v){
+ // 判断当前对列是否为空
+ // 如果push的数值大于入口元素的数值，那么就将队列后端的数值弹出，直到push的数值小于等于队列入口元素的数值为止。
+ // 这样就保持了队列里的数值是单调从大到小的了。
+ while (!$this->queue->isEmpty() && $v > $this->queue->top()) {
+ $this->queue->pop(); // pop从链表末尾弹出一个元素，
+ }
+ $this->queue->enqueue($v);
+ }
+
+ // 查询当前队列里的最大值 直接返回队首
+ public function max(){
+ // bottom 从链表前端查看元素, top从链表末尾查看元素
+ return $this->queue->bottom();
+ }
+
+ // 辅助理解: 打印队列元素
+ public function println(){
+ // "迭代器移动到链表头部": 可理解为从头遍历链表元素做准备。
+ // 【PHP中没有指针概念，所以就没说指针。从数据结构上理解，就是把指针指向链表头部】
+ $this->queue->rewind();
+
+ echo "Println: ";
+ while($this->queue->valid()){
+ echo $this->queue->current()," -> ";
+ $this->queue->next();
+ }
+ echo "\n";
+ }
+}
+```
+
-----------------------
diff --git a/problems/0538.把二叉搜索树转换为累加树.md b/problems/0538.把二叉搜索树转换为累加树.md
index 853cca6f..5c1e9e8c 100644
--- a/problems/0538.把二叉搜索树转换为累加树.md
+++ b/problems/0538.把二叉搜索树转换为累加树.md
@@ -352,6 +352,24 @@ function convertBST(root: TreeNode | null): TreeNode | null {
};
```
+## Scala
+
+```scala
+object Solution {
+ def convertBST(root: TreeNode): TreeNode = {
+ var sum = 0
+ def convert(node: TreeNode): Unit = {
+ if (node == null) return
+ convert(node.right)
+ sum += node.value
+ node.value = sum
+ convert(node.left)
+ }
+ convert(root)
+ root
+ }
+}
+```
-----------------------
diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md
index 6ee11eef..42e3fc09 100644
--- a/problems/0707.设计链表.md
+++ b/problems/0707.设计链表.md
@@ -104,8 +104,9 @@ public:
// 在第index个节点之前插入一个新节点，例如index为0，那么新插入的节点为链表的新头节点。
// 如果index 等于链表的长度，则说明是新插入的节点为链表的尾结点
// 如果index大于链表的长度，则返回空
+ // 如果index小于0，则置为0，作为链表的新头节点。
void addAtIndex(int index, int val) {
- if (index > _size) {
+ if (index > _size || index < 0) {
return;
}
LinkedNode* newNode = new LinkedNode(val);
diff --git a/problems/0977.有序数组的平方.md b/problems/0977.有序数组的平方.md
index 4052c570..458107dd 100644
--- a/problems/0977.有序数组的平方.md
+++ b/problems/0977.有序数组的平方.md
@@ -420,6 +420,24 @@ object Solution {
}
```
-
+C#：
+```csharp
+public class Solution {
+ public int[] SortedSquares(int[] nums) {
+ int k = nums.Length - 1;
+ int[] result = new int[nums.Length];
+ for (int i = 0, j = nums.Length - 1;i <= j;){
+ if (nums[i] * nums[i] < nums[j] * nums[j]) {
+ result[k--] = nums[j] * nums[j];
+ j--;
+ } else {
+ result[k--] = nums[i] * nums[i];
+ i++;
+ }
+ }
+ return result;
+ }
+}
+```
-----------------------
diff --git a/problems/背包理论基础01背包-1.md b/problems/背包理论基础01背包-1.md
index a40a92ab..e24824b9 100644
--- a/problems/背包理论基础01背包-1.md
+++ b/problems/背包理论基础01背包-1.md
@@ -356,9 +356,13 @@ func test_2_wei_bag_problem1(weight, value []int, bagweight int) int {
// 递推公式
for i := 1; i < len(weight); i++ {
//正序,也可以倒序
- for j := weight[i];j<= bagweight ; j++ {
- dp[i][j] = max(dp[i-1][j], dp[i-1][j-weight[i]]+value[i])
- }
+ for j := 0; j <= bagweight; j++ {
+ if j < weight[i] {
+ dp[i][j] = dp[i-1][j]
+ } else {
+ dp[i][j] = max(dp[i-1][j], dp[i-1][j-weight[i]]+value[i])
+ }
+ }
}
return dp[len(weight)-1][bagweight]
}
