题目描述
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]
提示:
1 <= values <= 10000
最多会对 appendTail、deleteHead 进行 10000 次调用
算法1
C++ 代码
class CQueue {
public:
stack<int> stN;
stack<int> stR;
int curr ;
CQueue() {
while (!stN.empty()) {
stN.pop();
}
while (!stR.empty()) {
stR.pop();
}
}
void appendTail(int value) {
stN.push(value);
}
int deleteHead() {
while(!stN.empty()){
int val = stN.top();stN.pop();
stR.push(val);
}
int ret = -1;
if(!stR.empty()){
ret = stR.top(); stR.pop();
}
while(!stR.empty()){
int val = stR.top(); stR.pop();
stN.push(val);
}
return ret;
}
};
/**
* Your CQueue object will be instantiated and called as such:
* CQueue* obj = new CQueue();
* obj->appendTail(value);
* int param_2 = obj->deleteHead();
*/