【leetcode】Min Stack（easy）

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.

思路：用栈

class MinStack {

public:

    void push(int x) {

        if(mins.empty() || x <= mins.top())

            mins.push(x);

        s.push(x);

    }



    void pop() {

        if(!s.empty() && !mins.empty() && s.top() == mins.top())

            mins.pop();

        s.pop();

    }



    int top() {

        return s.top();

    }



    int getMin() {

        return mins.top();

    }

private:

    stack<int> s;

    stack<int> mins;

};