min-stack

Min Stack – LeetCode 155

Problem

Description

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.

Example

MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); –> Returns -3.
minStack.pop();
minStack.top(); –> Returns 0.
minStack.getMin(); –> Returns -2.

Answer

Original

Code

class MinStack {
public:
    /** initialize your data structure here. */
    MinStack() {
    }
    
    void push(int x) {
        if(s.empty() || x <= min.top()) {s.push(x); min.push(x);}
        else {s.push(x);}
    }
    
    void pop() {
        if(s.top() == min.top()) {s.pop();min.pop();}
        else s.pop();
    }
    
    int top() {
        return s.top();
    }
    
    int getMin() {
        return min.top();
    }
private:
    stack<int> s,min;
};

思路

看题说话，用一个min来保持当前的最小值即可。
耗时$26$ ms，排名$33.71\%$

Better

还没看到更好的实现。