155.cpp

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

/**
 * 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();
 */