leetcode[155]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.

class MinStack {
private:
    stack<int> sta;
    stack<int> minsta;
public:
    void push(int x) {
        sta.push(x);
        if(minsta.empty()||(!minsta.empty()&&x<=minsta.top()))
        minsta.push(x);
    }

    void pop() {
        if(sta.empty())return;
        if(sta.top()==minsta.top())minsta.pop();
        sta.pop();
    }

    int top() {
        if(sta.empty())return INT_MAX;
        return sta.top();
    }

    int getMin() {
        if(minsta.empty())return INT_MAX;
        return minsta.top();
    }
};