155. Min Stack

class MinStack {
public:
    /** initialize your data structure here. */
    MinStack() {
    }

    void push(int x) {
        s1.push(x);
        if(s2.empty())
            s2.push(x);
        else
            s2.push(x<s2.top()?x:s2.top());
    }

    void pop() {
        s1.pop();
        s2.pop();
    }

    int top() {
        return s1.top();
    }

    int getMin() {
        return s2.top();
    }
private:
    stack<int> s1,s2;
};

class MinStack {
public:
    /** initialize your data structure here. */
    MinStack() {
    sta=INT_MAX;
    }

    void push(int x) {
        if(x<=sta){
            s1.push(sta);
            sta=x;
        }
        s1.push(x);
    }

    void pop() {
        int t=s1.top();s1.pop();
        if(t==sta){
            sta=s1.top();
            s1.pop();
        }
    }

    int top() {
        return s1.top();
    }

    int getMin() {
        return sta;
    }
private:
    int sta;
    stack<int> s1;
};