[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;
}