leetcode:min stack

class MinStack {
private:
    stack<int> s,minStack;
public:
    void push(int x) {
        s.push(x);
        if (minStack.empty() || x<=minStack.top())
        {
            minStack.push(x);
        }
    }

    void pop() {
        if (!minStack.empty() && s.top()==minStack.top())
            minStack.pop();
        s.pop();
    }

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

    int getMin() {
         return minStack.top();
    }

};