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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 toppeek/pop from topsize, 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).
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    class MyQueue {
        Stack<Integer> stack = new Stack<Integer>();
        // Push element x to the back of queue.
        public void push(int x) {
            stack.add(x);
        }
    
        // Removes the element from in front of queue.
        public void pop() {
            stack.remove(0);
        }
    
        // Get the front element.
        public int peek() {
            return stack.get(0);
        }
    
        // Return whether the queue is empty.
        public boolean empty() {
            return stack.isEmpty();
        }
    }
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  • 原文地址:https://www.cnblogs.com/hygeia/p/5123256.html
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