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  • Implement Queue using Stacks

    Implement the following operations of a queue using stacks.

    push(x) – Push element x to the back of queue.
    pop() – Removes the element from in front of queue.
    peek() – Get the front element.
    empty() – Return whether the queue is empty.
    Notes:
    You must use only standard operations of a stack – which means only push to top, peek/pop from top, size, and is empty operations are valid.
    Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
    You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

    class Queue {
    
    
    public:
         stack<int>res;
        // Push element x to the back of queue.
        void push(int x) {
            stack<int>test;
    
            while(res.empty()!=true)
            {
                test.push(res.top());
                res.pop();
            }
            test.push(x);
            while(test.empty()!=true)
            {
                 res.push(test.top());
                 test.pop();
            }
    
        }
    
        // Removes the element from in front of queue.
        void pop(void) {
         res.pop();
        }
    
        // Get the front element.
        int peek(void) {
            return res.top();
        }
    
        // Return whether the queue is empty.
        bool empty(void) {
            return res.empty();
        }
    };
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  • 原文地址:https://www.cnblogs.com/djiankuo/p/5008696.html
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