【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.

 

class MinStack {
private:
    stack<int> stk;
    stack<int> minstack;
public:
    void push(int x) {
        stk.push(x);
        if(minstack.empty())
        {
            minstack.push(x);
        }else
        {
            if(x<=minstack.top())
                minstack.push(x);
        }
    }

    void pop() {
        if(stk.top()==minstack.top())
        {
            stk.pop();
            minstack.pop();
        }else
        {
            stk.pop();
        }
    }

    int top() {
        return stk.top();
    }

    int getMin() {
        return minstack.top();
    }
};