题目描述

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样例

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算法1

(暴力枚举) $O(n^2)$

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时间复杂度

参考文献

C++ 代码

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算法2

(暴力枚举) $O(n^2)$

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时间复杂度

参考文献

C++ 代码

class MyQueue {
public:
    /** Initialize your data structure here. */
    // 用两个栈 一个栈作为缓冲栈,当需要pop和peek的时候，先倒到缓冲栈，完成操作后再倒回来
    stack<int> s1,s2;
    MyQueue() {

    }

    /** Push element x to the back of queue. */
    void push(int x) {
        s1.push(x);
    }

    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        while(!s1.empty()){
            s2.push(s1.top());
            s1.pop();
        }
        int tmp = s2.top();
        s2.pop();
        while(!s2.empty()){
            s1.push(s2.top());
            s2.pop();
        }
        return tmp;
    }

    /** Get the front element. */
    int peek() {
        while(!s1.empty()){
            s2.push(s1.top());
            s1.pop();
        }
        int tmp = s2.top();
        while(!s2.empty()){
            s1.push(s2.top());
            s2.pop();
        }
        return tmp;
    }

    /** Returns whether the queue is empty. */
    bool empty() {
        return s1.empty();
    }
};

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