leetCode(45):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 {
public:
    void push(int x) {
        data.push(x);//数据栈正常压入
        if(minData.empty())
        {//最小栈数据栈压入时要进行推断。假设被压入的数据不影响最小值，则直接再压入

//最小栈栈顶元素，否则压入x
            minData.push(x);
        }
        else
        {
            if(x<minData.top())
            {
                minData.push(x);
            }
            else
            {
                minData.push(minData.top());
            }
        }
    }

    void pop() {//弹出时，两个栈都须要弹出
        data.pop();
        minData.pop();
    }

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

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

private:
    stack<int> data;
    stack<int> minData;
};