Leetcode 155. 最小栈

A就是正常的栈
m存放入(出)栈每次最小值发生变化的临界点

class MinStack {
public:
    /** initialize your data structure here. */
    vector A,m;
    MinStack() {

    }

    void push(int x) {
        A.push_back(x);
        if(m.empty() || x<=m.back()) m.push_back(x);
    }

    void pop() {
        if(m.back()==A.back())  m.pop_back();
        A.pop_back();
    }

    int top() {
        return A.back();
    }

    int getMin() {
        return m.back();
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(x);
 * obj.pop();
 * int param_3 = obj.top();
 * int param_4 = obj.getMin();
 */