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Problem
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 )
Example1
输入:
[“CQueue”,“appendTail”,“deleteHead”,“deleteHead”]
[[],[3],[],[]]
输出:[null,null,3,-1]
Example2
输入:
[“CQueue”,“deleteHead”,“appendTail”,“appendTail”,“deleteHead”,“deleteHead”]
[[],[],[5],[2],[],[]]
输出:[null,-1,null,null,5,2]
Solution
class CQueue {
public:CQueue() {}void appendTail(int value) {s1.push(value);}int deleteHead() {if(!s2.empty()){int ret = s2.top();s2.pop();return ret;}else{if(s1.empty())return -1;else{while(s1.size() > 1){int tmp = s1.top();s1.pop();s2.push(tmp);}int tmp = s1.top();s1.pop();return tmp;}}}
private:stack<int> s1;stack<int> s2;
};/*** Your CQueue object will be instantiated and called as such:* CQueue* obj = new CQueue();* obj->appendTail(value);* int param_2 = obj->deleteHead();*/
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