my-leetcode/232.implement-queue-using-stacks.cpp at main · IamPurpleRed/my-leetcode · GitHub

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/*
 * @lc app=leetcode id=232 lang=cpp
 *
 * [232] Implement Queue using Stacks
 */

// @lc code=start
class MyQueue {
  private:
    stack<int> input, output;

  public:
    MyQueue() {
    }

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

    int pop() {
        int value = peek();
        output.pop();
        return value;
    }

    int peek() {
        if (output.empty()) {
            while (!input.empty()) {
                output.push(input.top());
                input.pop();
            }
        }
        return output.top();
    }

    bool empty() {
        return (input.empty() && output.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();
 */
// @lc code=end