用两个栈实现一个队列。队列的声明如下,请实现它的两个函数 appendTail 和 deleteHead ,分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素,deleteHead 操作返回 -1 )
输入:
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出:[null,null,3,-1]
先上代码
import java.util.LinkedList;
import java.util.Stack;
/**
* @author DBC
* @date 2022/5/26 10:23
* @network dbc655.top
*/
class CQueue {
LinkedList<Integer> A, B;
public CQueue() {
A = new LinkedList<Integer>();
B = new LinkedList<Integer>();
}
public void appendTail(int value) {
A.addLast(value);
}
public int deleteHead() {
if(!B.isEmpty()) {
return B.removeLast();
}
if(A.isEmpty()) {
return -1;
}
while(!A.isEmpty()) {
B.addLast(A.removeLast());
}
return B.removeLast();
}
}