LeetCode/232.cpp at main · vys1n/LeetCode · GitHub

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#include <stack>
using namespace std;

class MyQueue {
    stack<int> s1, s2;
public:
    MyQueue() {}

    void push(int x) {
        s1.push(x);
    }

    int pop() {
        if (s2.empty()) {
            while(!s1.empty()) {
                s2.push(s1.top());
                s1.pop();
            }
        }

        int res = s2.top();
        s2.pop();
        return res;
    }

    int peek() {
        if (s2.empty()) {
            while(!s1.empty()) {
                s2.push(s1.top());
                s1.pop();
            }
        }

        return s2.top();
    }

    bool empty() {
        return s1.empty() && s2.empty();
    }
};