题目
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 )
示例 1:
输入:
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出:[null,null,3,-1]
示例 2:
输入:
["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
[[],[],[5],[2],[],[]]
输出:[null,-1,null,null,5,2]
解题
和leetcode-232:用栈实现队列一样,只不过,这道题,只需要实现增、删
class CQueue {
public:
stack<int> st1;
stack<int> st2;
CQueue() {
}
void appendTail(int value) {
while(!st1.empty()){
st2.push(st1.top());
st1.pop();
}
st1.push(value);
while(!st2.empty()){
st1.push(st2.top());
st2.pop();
}
}
int deleteHead() {
if(st1.empty()) return -1;
int num=st1.top();
st1.pop();
return num;
}
};