Merge pull request #1498 from UndeadSheep/master

新增 栈与队列部分的 C#版

problems/0020.有效的括号.md

@@ -402,6 +402,38 @@ bool isValid(char * s){
 ```
 
 
+C#:
+```csharp
+public class Solution {
+    public bool IsValid(string s) {
+        var len = s.Length;
+        if(len % 2 == 1) return false; // 字符串长度为单数，直接返回 false
+        // 初始化栈
+        var stack = new Stack<char>();
+        // 遍历字符串
+        for(int i = 0; i < len; i++){
+            // 当字符串为左括号时，进栈对应的右括号
+            if(s[i] == '('){
+                stack.Push(')');
+            }else if(s[i] == '['){
+                stack.Push(']');
+            }else if(s[i] == '{'){
+                stack.Push('}');
+            }
+            // 当字符串为右括号时，当栈为空（无左括号） 或者 出栈字符不是当前的字符
+            else if(stack.Count == 0 || stack.Pop() != s[i])
+                return false;
+        }
+        // 如果栈不为空，例如“((()”，右括号少于左括号，返回false
+        if (stack.Count > 0)
+            return false;
+        // 上面的校验都满足，则返回true
+        else
+            return true;
+    }
+}
+```
+
 PHP:
 ```php
 // https://www.php.net/manual/zh/class.splstack.php

problems/0150.逆波兰表达式求值.md

@@ -326,6 +326,40 @@ func evalRPN(_ tokens: [String]) -> Int {
 }
 ```
 
+C#:
+```csharp
+public int EvalRPN(string[] tokens) {
+        int num;
+        Stack<int> stack = new Stack<int>();
+        foreach(string s in tokens){
+           if(int.TryParse(s, out num)){
+                stack.Push(num);
+            }else{
+                int num1 = stack.Pop();
+                int num2 = stack.Pop();
+                switch (s)
+                {
+                    case "+":
+                        stack.Push(num1 + num2);
+                        break;
+                    case "-":
+                        stack.Push(num2 - num1);
+                        break;
+                    case "*":
+                        stack.Push(num1 * num2);
+                        break;
+                    case "/":
+                        stack.Push(num2 / num1);
+                        break;
+                    default:
+                        break;
+                }
+            }
+        }
+        return stack.Pop(); 
+    }
+```
+
 
 PHP：
 ```php

problems/0225.用队列实现栈.md

@@ -900,6 +900,41 @@ class MyStack() {
 ```
 
 
+C#:
+```csharp
+public class MyStack {
+    Queue<int> queue1;
+    Queue<int> queue2;
+    public MyStack() {
+        queue1 = new Queue<int>();
+        queue2 = new Queue<int>();
+    }
+    
+    public void Push(int x) {
+        queue2.Enqueue(x);
+        while(queue1.Count != 0){
+            queue2.Enqueue(queue1.Dequeue());
+        }
+        Queue<int> queueTemp;
+        queueTemp = queue1;
+        queue1 = queue2;
+        queue2 = queueTemp;
+    }
+    
+    public int Pop() {
+        return queue1.Count > 0 ? queue1.Dequeue() : -1;
+    }
+    
+    public int Top() {
+        return queue1.Count > 0 ? queue1.Peek() : -1;
+    }
+    
+    public bool Empty() {
+        return queue1.Count == 0;
+    }
+}
+```
+
 PHP
 > 双对列
 ```php

problems/0232.用栈实现队列.md

@@ -497,6 +497,49 @@ void myQueueFree(MyQueue* obj) {
 ```
 
 
+C#:
+```csharp
+public class MyQueue {
+    Stack<int> inStack;
+    Stack<int> outStack;
+
+    public MyQueue() {
+        inStack = new Stack<int>();// 负责进栈
+        outStack = new Stack<int>();// 负责出栈
+    }
+    
+    public void Push(int x) {
+        inStack.Push(x);
+    }
+    
+    public int Pop() {
+        dumpstackIn();
+        return outStack.Pop();
+    }
+    
+    public int Peek() {
+        dumpstackIn();
+        return outStack.Peek();
+    }
+    
+    public bool Empty() {
+        return inStack.Count == 0 && outStack.Count == 0;
+    }
+
+    // 处理方法：
+    // 如果outStack为空，那么将inStack中的元素全部放到outStack中
+    private void dumpstackIn(){
+        if (outStack.Count != 0) return; 
+        while(inStack.Count != 0){
+            outStack.Push(inStack.Pop());
+        }
+    }
+}
+
+```
+
+
+
 PHP:
 ```php
 // SplStack 类通过使用一个双向链表来提供栈的主要功能。[PHP 5 >= 5.3.0, PHP 7, PHP 8]
@@ -583,5 +626,6 @@ class MyQueue() {
 
 }
 ```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0239.滑动窗口最大值.md

@@ -756,5 +756,46 @@ class MyQueue{
 }
 ```
 
+C#:
+```csharp
+class myDequeue{
+        private LinkedList<int> linkedList = new LinkedList<int>();
+
+        public void Enqueue(int n){
+            while(linkedList.Count > 0 && linkedList.Last.Value < n){
+                linkedList.RemoveLast();
+            }
+            linkedList.AddLast(n);
+        }
+
+        public int Max(){
+            return linkedList.First.Value;
+        }
+
+        public void Dequeue(int n){
+            if(linkedList.First.Value == n){
+                linkedList.RemoveFirst();
+            }   
+        }
+    }
+
+    myDequeue window = new myDequeue();
+    List<int> res = new List<int>();
+
+    public int[] MaxSlidingWindow(int[] nums, int k) {
+        for(int i = 0; i < k; i++){
+            window.Enqueue(nums[i]);
+        }
+        res.Add(window.Max());
+        for(int i = k; i < nums.Length; i++){
+            window.Dequeue(nums[i-k]);
+            window.Enqueue(nums[i]);
+            res.Add(window.Max());
+        }
+
+        return res.ToArray();
+    }
+```
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0347.前K个高频元素.md

@@ -371,6 +371,44 @@ function topKFrequent(nums: number[], k: number): number[] {
 };
 ```
 
+C#:
+```csharp
+ public int[] TopKFrequent(int[] nums, int k) {
+        //哈希表-标权重
+        Dictionary<int,int> dic = new();
+        for(int i = 0; i < nums.Length; i++){
+            if(dic.ContainsKey(nums[i])){
+                dic[nums[i]]++;
+            }else{
+                dic.Add(nums[i], 1);
+            }
+        }
+        //优先队列-从小到大排列
+        PriorityQueue<int,int> pq = new();
+        foreach(var num in dic){
+            pq.Enqueue(num.Key, num.Value);
+            if(pq.Count > k){
+                pq.Dequeue();
+            }
+        }
+        
+        // //Stack-倒置
+        // Stack<int> res = new();
+        // while(pq.Count > 0){
+        //     res.Push(pq.Dequeue());
+        // }
+        // return res.ToArray();
+
+        //数组倒装
+        int[] res = new int[k];
+        for(int i = k - 1; i >= 0; i--){
+            res[i] = pq.Dequeue();
+        }
+        return res;
+    }
+    
+```
+
 Scala:
 
 解法一: 优先级队列
@@ -413,6 +451,7 @@ object Solution {
       .map(_._1)
   }
 }
+
 ```
 
 -----------------------

problems/1047.删除字符串中的所有相邻重复项.md

@@ -376,6 +376,25 @@ func removeDuplicates(_ s: String) -> String {
 ```
 
 
+C#:
+```csharp
+public string RemoveDuplicates(string s) {
+        //拿字符串直接作为栈，省去了栈还要转为字符串的操作
+        StringBuilder res = new StringBuilder();
+
+        foreach(char c in s){
+            if(res.Length > 0 && res[res.Length-1] == c){
+                res.Remove(res.Length-1, 1);
+            }else{
+                res.Append(c);
+            }
+        }
+       
+        return res.ToString();
+    }
+```
+
+
 PHP:
 ```php
 class Solution {