用两个栈实现队列

package leetcode.剑指Offer.用两个栈实现队列;

import java.util.Stack;

public class LeetCode {
    public static void main(String[] args) {
    }
}

class CQueue {
    Stack<Integer> stack1 = new Stack<>();
    Stack<Integer> stack2 = new Stack<>();

    public CQueue() {}

    public void appendTail(int value) {
        stack1.push(value);
    }

    public int deleteHead() {
        if (stack1.isEmpty() && stack2.isEmpty()) {
            return -1;
        }

        if (stack2.isEmpty()) {
            while (!stack1.isEmpty()) {
                stack2.push(stack1.pop());
            }
        }

        return stack2.pop();
    }
}

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