155. Min Stack.cpp

#include <stack>
using namespace std;
class MinStack
{
public:
    MinStack()
    {
    }

    void push(int val)
    {
        if (st.empty() || val < st.top().second)
            st.push({val, val});
        else
            st.push({val, st.top().second});
    }

    void pop()
    {
        st.pop();
    }

    int top()
    {
        return st.top().first;
    }

    int getMin()
    {
        return st.top().second;
    }

private:
    stack<pair<int, int>> st;
};

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