0232_Implement_Queue_using_Stacks.cpp

#pragma GCC optimize("Ofast","inline","ffast-math","unroll-loops","no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native","f16c")
class MyQueue {
public:
    stack<int>s1;
    stack<int>s2; 
    MyQueue() {
        
    }
    
    void push(int x) {
        s1.push(x);
    }
    
    int pop() {
        if(s2.empty()){
            while(!s1.empty()){
                s2.push(s1.top());
                s1.pop();
            }
        }
        int ans=s2.top();
        s2.pop();
        return ans;
    }
    
    int peek() {
        if(s2.empty()){
            while(!s1.empty()){
                s2.push(s1.top());
                s1.pop();
            }
        }
        return s2.top();
    }
    
    bool empty() {
        return s1.empty() && s2.empty();
    }
};

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue* obj = new MyQueue();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->peek();
 * bool param_4 = obj->empty();
 */