Merge branch 'youngyangyang04:master' into master

problems/0015.三数之和.md

@@ -493,6 +493,9 @@ function threeSum(nums: number[]): number[][] {
         right: number = length - 1;
     let resArr: number[][] = [];
     for (let i = 0; i < length; i++) {
+    	if (nums[i]>0) {
+            return resArr; //nums经过排序后，只要nums[i]>0, 此后的nums[i] + nums[left] + nums[right]均大于0,可以提前终止循环。	
+	}
         if (i > 0 && nums[i] === nums[i - 1]) {
             continue;
         }

problems/0019.删除链表的倒数第N个节点.md

@@ -191,18 +191,20 @@ TypeScript:
 ```typescript
 function removeNthFromEnd(head: ListNode | null, n: number): ListNode | null {
     let newHead: ListNode | null = new ListNode(0, head);
-    let slowNode: ListNode | null = newHead,
-        fastNode: ListNode | null = newHead;
-    for (let i = 0; i < n; i++) {
-        fastNode = fastNode.next;
+    //根据leetcode题目的定义可推断这里快慢指针均不需要定义为ListNode | null。
+    let slowNode: ListNode = newHead;
+    let fastNode: ListNode = newHead;
+
+    while(n--) {
+        fastNode = fastNode.next!; //由虚拟头节点前进n个节点时,fastNode.next可推断不为null。
     }
-    while (fastNode.next) {
+    while(fastNode.next) {  //遍历直至fastNode.next = null， 即尾部节点。 此时slowNode指向倒数第n个节点。
         fastNode = fastNode.next;
-        slowNode = slowNode.next;
+        slowNode = slowNode.next!;
     }
-    slowNode.next = slowNode.next.next;
+    slowNode.next = slowNode.next!.next; //倒数第n个节点可推断其next节点不为空。 
     return newHead.next; 
-};
+}
 ```
 
 版本二（计算节点总数法）：

problems/0096.不同的二叉搜索树.md

@@ -252,6 +252,24 @@ function numTrees(n: number): number {
 };
 ```
 
+### Rust
+
+```Rust
+impl Solution {
+    pub fn num_trees(n: i32) -> i32 {
+        let n = n as usize;
+        let mut dp = vec![0; n + 1];
+        dp[0] = 1;
+        for i in 1..=n {
+            for j in 1..=i {
+                dp[i] += dp[j - 1] * dp[i - j];
+            }
+        }
+        dp[n]
+    }
+}
+```
+
 ### C
 
 ```c

problems/0203.移除链表元素.md

@@ -385,7 +385,8 @@ function removeElements(head: ListNode | null, val: number): ListNode | null {
         if (cur.val === val) {
             pre.next = cur.next;
         } else {
-            pre = pre.next;
+            //此处不加类型断言时：编译器会认为pre类型为ListNode, pre.next类型为ListNode | null
+            pre = pre.next as ListNode;
         }
         cur = cur.next;
     }

problems/0343.整数拆分.md

@@ -299,6 +299,27 @@ function integerBreak(n: number): number {
 };
 ```
 
+### Rust
+
+```Rust
+impl Solution {
+    fn max(a: i32, b: i32) -> i32{
+        if a > b { a } else { b }
+    }
+    pub fn integer_break(n: i32) -> i32 {
+        let n = n as usize;
+        let mut dp = vec![0; n + 1];
+        dp[2] = 1;
+        for i in 3..=n {
+            for j in 1..i - 1 {
+                dp[i] = Self::max(dp[i], Self::max(((i - j) * j) as i32, dp[i - j] * j as i32));
+            }
+        }
+        dp[n]
+    }
+}
+```
+
 ### C
 
 ```c

problems/0376.摆动序列.md

@@ -266,22 +266,58 @@ class Solution:
 
 ### Go 
 
+**贪心**
 ```golang
 func wiggleMaxLength(nums []int) int {
-    var count,preDiff,curDiff  int
-    count=1
-    if len(nums)<2{
-        return count
-    }
-    for i:=0;i<len(nums)-1;i++{
-        curDiff=nums[i+1]-nums[i]
-        //如果有正有负则更新下标值||或者只有前一个元素为0（针对两个不等元素的序列也视作摆动序列，且摆动长度为2）
-        if (curDiff > 0 && preDiff <= 0) || (preDiff >= 0 && curDiff < 0){
-            preDiff=curDiff
-            count++
-        }
-    }
-    return count
+	var count, preDiff, curDiff int //初始化默认为0
+	count = 1                       // 初始化为1，因为最小的序列是1个数
+	if len(nums) < 2 {
+		return count
+	}
+	for i := 0; i < len(nums)-1; i++ {
+		curDiff = nums[i+1] - nums[i]
+		if (curDiff > 0 && preDiff <= 0) || (curDiff < 0 && preDiff >= 0) {
+			count++
+		}
+	}
+	return count
+}
+```
+
+**动态规划**
+```golang
+func wiggleMaxLength(nums []int) int {
+	n := len(nums)
+	if n <= 1 {
+		return n
+	}
+	dp := make([][2]int, n)
+	//  i 0 作为波峰的最大长度
+	//  i 1 作为波谷的最大长度
+	dp[0][0] = 1
+	dp[0][1] = 1
+	for i := 0; i < n; i++ {
+		for j := 0; j < i; j++ {
+			if nums[j] > nums[i] { //nums[i]为波谷
+				dp[i][1] = max(dp[i][1], dp[j][0]+1)
+			}
+			if nums[j] < nums[i] { //nums[i]为波峰 或者相等
+				dp[i][0] = max(dp[i][0], dp[j][1]+1)
+			}
+			if nums[j] == nums[i] { //添加一种情况，nums[i]为相等
+				dp[i][0] = max(dp[i][0], dp[j][0]) //波峰
+				dp[i][1] = max(dp[i][1], dp[j][1]) //波谷
+			}
+		}
+	}
+	return max(dp[n-1][0], dp[n-1][1])
+}
+func max(a, b int) int {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
 }
 ```
 

problems/0714.买卖股票的最佳时机含手续费（动态规划）.md

@@ -221,8 +221,46 @@ function maxProfit(prices: number[], fee: number): number {
 };
 ```
 
+Rust:
+**贪心**
+```Rust
+impl Solution {
+    pub fn max_profit(prices: Vec<i32>, fee: i32) -> i32 {
+        let mut result = 0;
+        let mut min_price = prices[0];
+        for i in 1..prices.len() {
+            if prices[i] < min_price { min_price = prices[i]; }
 
+            // if prices[i] >= min_price && prices[i] <= min_price + fee { continue; }
 
+            if prices[i] > min_price + fee {
+                result += prices[i] - min_price - fee;
+                min_price = prices[i] - fee;
+            }
+        }
+        result
+    }
+}
+```
+
+**动态规划**
+```Rust
+impl Solution {
+    fn max(a: i32, b: i32) -> i32 {
+        if a > b { a } else { b }
+    }
+    pub fn max_profit(prices: Vec<i32>, fee: i32) -> i32 {
+        let n = prices.len();
+        let mut dp = vec![vec![0; 2]; n];
+        dp[0][0] -= prices[0];
+        for i in 1..n {
+            dp[i][0] = Self::max(dp[i - 1][0], dp[i - 1][1] - prices[i]);
+            dp[i][1] = Self::max(dp[i - 1][1], dp[i - 1][0] + prices[i] - fee);
+        }
+        Self::max(dp[n - 1][0], dp[n - 1][1])
+    }
+}
+```
 
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0738.单调递增的数字.md

@@ -278,5 +278,26 @@ object Solution {
 }
 ```
 
+### Rust
+
+```Rust
+impl Solution {
+    pub fn monotone_increasing_digits(n: i32) -> i32 {
+        let mut str_num = n.to_string().chars().map(|x| x.to_digit(10).unwrap() as i32).collect::<Vec<i32>>();
+        let mut flag = str_num.len();
+        for i in (1..str_num.len()).rev() {
+            if str_num[i - 1] > str_num[i] {
+                flag = i;
+                str_num[i - 1] -= 1;
+            }
+        }
+        for i in flag..str_num.len() {
+            str_num[i] = 9;
+        }
+        str_num.iter().fold(0, |acc, x| acc * 10 + x)
+    }
+}
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/链表理论基础.md

@@ -186,7 +186,7 @@ TypeScript:
 ```typescript
 class ListNode {
   public val: number;
-  public next: ListNode = null;
+  public next: ListNode|null = null;
   constructor(value: number) {
     this.val = value;
     this.next = null;