Leetcode Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.

• getMin() -- Retrieve the minimum element in the stack.

  设计一个栈，使得它有如下功能：出栈，入栈，获得栈顶元素，获得最小元素，时间复杂度是O(1)，利用两个栈，一个负责存储元素，一个负责存储最小元素。

• class MinStack {public:    stack<int> stack1;    stack<int> stack2;    void push(int x) {        stack1.push(x);        if(stack2.empty())        {            stack2.push(x);        }        else        {            if(x<=stack2.top())            {                stack2.push(x);            }        }    }    void pop() {        if(stack1.top() == stack2.top())        {            stack2.pop();        }        stack1.pop();    }    int top() {        return stack1.top();    }    int getMin() {        return stack2.top();    }};