Update 155.min-stack.md

problems/155.min-stack.md

@@ -64,7 +64,7 @@ pop或者top的时候：
 
 ## 代码
 
-* 语言支持：JS，Python
+* 语言支持：JS，C++，Java，Python
 
 Javascript Code:
 
@@ -139,6 +139,123 @@ MinStack.prototype.min = function() {
  */
 ```
 
+C++ Code:
+
+```c++
+class MinStack {
+    stack<long> data;
+    long min = INT_MAX;
+public:
+    /** initialize your data structure here. */
+    MinStack() {
+
+    }
+
+    void push(int x) {
+        data.push(x - min);
+        if(x < min)
+        {
+            min = x;
+        }
+
+    }
+
+    void pop() {
+        long top = data.top();
+        data.pop();
+        // 更新最小值
+        if(top < 0)
+        {
+            min -= top;
+        }
+
+    }
+
+    int top() {
+        long top = data.top();
+        // 最小值为 min
+        if (top < 0)
+        {
+            return min;
+        }
+        else{
+            return min+top;
+        }
+    }
+
+    int getMin() {
+        return min;
+    }
+};
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack* obj = new MinStack();
+ * obj->push(x);
+ * obj->pop();
+ * int param_3 = obj->top();
+ * int param_4 = obj->getMin();
+ */
+```
+
+
+Java Code:
+
+```java
+class MinStack {
+    long min;
+    Stack<Long> stack;
+
+    /** initialize your data structure here. */
+    public MinStack() {
+        stack = new Stack<>();
+    }
+
+    public void push(int x) {
+        if (stack.isEmpty()) {
+            stack.push(0L);
+            min = x;
+        }
+        else {
+            stack.push(x - min);
+            if (x < min)
+                min = x;
+        }
+    }
+
+    public void pop() {
+        long p = stack.pop();
+
+        if (p < 0) {
+            // if (p < 0), the popped value is the min
+            // Recall p is added by this statement: stack.push(x - min);
+            // So, p = x - old_min
+            // old_min = x - p
+            // again, if (p < 0), x is the min so:
+            // old_min = min - p
+            min = min - p;
+        }
+    }
+
+    public int top() {
+        long p = stack.peek();
+
+        if (p < 0) {
+            return (int) min;
+        }
+        else {
+            // p = x - min
+            // x = p + min
+            return (int) (p + min);
+        }
+    }
+
+    public int getMin() {
+        return (int) min;    
+    }
+}
+```
+
 Python Code:
 
 ```python
@@ -207,7 +324,7 @@ class MinStack:
 
 ## 代码
 
-JavaScript：
+JavaScript Code:
 
 ```js
 /**
@@ -263,8 +380,107 @@ MinStack.prototype.min = function() {
  */
 ```
 
+C++ Code:
+```c++
+class MinStack {
+    stack<int> data;
+    stack<int> helper;
+public:
+    /** initialize your data structure here. */
+    MinStack() {
+
+    }
+
+    void push(int x) {
+        data.push(x);
+        if(helper.empty() || helper.top() >= x)
+        {
+            helper.push(x);
+        }
+
+    }
+
+    void pop() {
+        int top = data.top();
+        data.pop();
+        if(top == helper.top())
+        {
+            helper.pop();
+        }
+
+    }
+
+    int top() {
+        return data.top();
+    }
+
+    int getMin() {
+        return helper.top();
+    }
+};
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack* obj = new MinStack();
+ * obj->push(x);
+ * obj->pop();
+ * int param_3 = obj->top();
+ * int param_4 = obj->getMin();
+ */
+```
+
+Java Code:
+```java
+public class MinStack {
+
+    // 数据栈
+    private Stack<Integer> data;
+    // 辅助栈
+    private Stack<Integer> helper;
+
+    /**
+     * initialize your data structure here.
+     */
+    public MinStack() {
+        data = new Stack<>();
+        helper = new Stack<>();
+    }
+
+    public void push(int x) {
+        // 辅助栈在必要的时候才增加
+        data.add(x);
+        if (helper.isEmpty() || helper.peek() >= x) {
+            helper.add(x);
+        }
+    }
+
+    public void pop() {
+        // 关键 3：data 一定得 pop()
+        if (!data.isEmpty()) {
+            // 注意：声明成 int 类型，这里完成了自动拆箱，从 Integer 转成了 int，
+            // 因此下面的比较可以使用 "==" 运算符
+            int top = data.pop();
+            if(top == helper.peek()){
+                helper.pop();
+            }
+        }
+    }
+
+    public int top() {
+        if(!data.isEmpty()){
+            return data.peek();
+        }
+    }
+
+    public int getMin() {
+        if(!helper.isEmpty()){
+            return helper.peek();
+        }
+    }
+}
+```
 
-Python3:
+Python3 Code:
 
 ```python
 class MinStack: