[LeetCode] Min Stack 栈

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.

 

 

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  Stack Data Structure

 

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　　这个是通过两个stack 维护，一个辅助栈support 维护非升序的情况，注意需要非升序，一个是用于全部data 维护。

 

#include <iostream>

#include <stack>

using namespace std;



class MinStack {

public:

    stack<int> data;

    stack<int> support;



    void push(int x) {

        if(data.empty()){

            data.push(x);

            support.push(x);

        }

        else{

            data.push(x);

            if(x<=support.top()) support.push(x);

        }

    }



    void pop() {

        if(data.top()==support.top())   support.pop();

        data.pop();

    }



    int top() {

        return data.top();

    }



    int getMin() {

        return support.top();

    }

};

int main()

{

    MinStack myMinStack;

    myMinStack.push(1);

    cout<<myMinStack.getMin()<<endl;

    myMinStack.push(2);

    cout<<myMinStack.getMin()<<endl;

    myMinStack.push(0);

    cout<<myMinStack.getMin()<<endl;

    myMinStack.pop();

    myMinStack.pop();

    cout<<myMinStack.getMin()<<endl;

    myMinStack.pop();

    return 0;

}