剑指offer——面试题9：用两个栈实现队列

#include "Queue.h"

// ====================测试代码====================
void Test(char actual, char expected)
{
    if(actual == expected)
        printf("Test passed.
");
    else
        printf("Test failed.
");
}

int main(int argc, char* argv[])
{
    CQueue<char> queue;

    queue.appendTail('a');
    queue.appendTail('b');
    queue.appendTail('c');

    char head = queue.deleteHead();
    Test(head, 'a');

    head = queue.deleteHead();
    Test(head, 'b');

    queue.appendTail('d');
    head = queue.deleteHead();
    Test(head, 'c');

    queue.appendTail('e');
    head = queue.deleteHead();
    Test(head, 'd');

    head = queue.deleteHead();
    Test(head, 'e');

    return 0;
}

QueueWithTwoStacks.cpp

 1 // 面试题9：用两个栈实现队列
 2 // 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
 3 // 和deleteHead，分别完成在队列尾部插入结点和在队列头部删除结点的功能。
 4 
 5 #pragma once
 6 #include <stack>
 7 #include <exception>
 8 #include<stdio.h>
 9 #include<stdexcept>
10 
11 using namespace std;
12 
13 template <typename T> class CQueue
14 {
15 public:
16     CQueue(void);
17     ~CQueue(void);
18 
19     // 在队列末尾添加一个结点
20     void appendTail(const T& node);
21 
22     // 删除队列的头结点
23     T deleteHead();
24 
25 private:
26     stack<T> stack1;
27     stack<T> stack2;
28 };
29 
30 template <typename T> CQueue<T>::CQueue(void)
31 {
32 }
33 
34 template <typename T> CQueue<T>::~CQueue(void)
35 {
36 }
37 
38 template<typename T> void CQueue<T>::appendTail(const T& element)
39 {
40     stack1.push(element);
41 }
42 
43 template<typename T> T CQueue<T>::deleteHead()
44 {
45     if(stack2.size()<= 0)
46     {
47         while(stack1.size()>0)
48         {
49             T& data = stack1.top();
50             stack1.pop();
51             stack2.push(data);
52         }
53     }
54 
55     if(stack2.size() == 0){
56         std::logic_error ex("queue is empty");
57         throw std::exception(ex);
58     }
59 
60     T head = stack2.top();
61     stack2.pop();
62 
63     return head;
64 }

Queue.h