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]
class CQueue {
public:
CQueue() {}
void appendTail(int value) {
stack1.push(value);
}
int deleteHead() {
if(!stack2.empty())
{
int s = stack2.top();
stack2.pop();
return s;
}
else
{
while(!stack1.empty())
{
stack2.push(stack1.top());
stack1.pop();
}
if(stack2.empty())
return -1;
int a = stack2.top();
stack2.pop();
return a;
}
}
private:
stack stack1;
stack stack2;
};
/**
* Your CQueue object will be instantiated and called as such:
* CQueue* obj = new CQueue();
* obj->appendTail(value);
* int param_2 = obj->deleteHead();
*/
Original: https://www.cnblogs.com/hitwherznchjy/p/16541899.html
Author: 静候佳茵
Title: 剑指 Offer 09. 用两个栈实现队列
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