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coding interviews 05 用栈实现队列

admin 11月 13, 2020 0

题目描述

用两个栈来实现一个队列，完成队列的Push和Pop操作。队列中的元素为int类型。

思路

use two stack to realize a queue, which is equal to realize “first in first out”.
We need to realize the funcion of push and pop:
step1: the push of queue: just push into stack 1.
step2: the pop of the queue:
1.if there is element in stack 2, pop it.
2.if not, pop all element in stack2 and then pop.

代码

public class QueueWithTwoStack {
    
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();
    
    public void push(int node) {
        stack1.push(node);
    }
    
    public int () {
        
        if(!stack2.isEmpty()){
            return stack2.pop();
        }else{
            //let stack1 go to stack2
            while(!stack1.isEmpty()){
                stack2.push(stack1.pop());
            }
            return stack2.pop();
        }
        
    }
}