【编程珠玑】读书笔记 第五章 编程小事

2013-07-14 14:41:31

本章主要讨论如何根据伪代码编写程序，并用脚手架测试程序的正确性。

作者使用脚手架这个名词，刚开始看，真看不懂，估计是语言习惯的问题，看完这一章，才大致明白就是测试代码所搭建的程序。

书中的脚手架主要是采用assert进行测试，自己觉得很不习惯。

下面是自己写的二分搜索的递归以及非递归实现，并附上测试结果。

完整代码：

#include <iostream>
using namespace std;

#define SIZE 100

//递归implementation
//int _bsearch_recursive(const int a_unsorted[],size_t begin,size_t end,int x)   //不要用size_t类型
int _bsearch_recursive(const int a_unsorted[],int begin,int end,int x)
{
    //size_t mid = (begin + end)/2;
    if (begin > end)  
    {
        return -1;
    }

    int mid = (begin + end)/2;

    if ( x == a_unsorted[mid] )
    {
        return mid;
    }

    if ( x < a_unsorted[mid] )
    {
        return _bsearch_recursive(a_unsorted,begin,mid - 1,x);
    }
        
    return _bsearch_recursive(a_unsorted,mid + 1,end,x);  
}

int _bsearch_1(const int a_unsorted[],size_t n,int x)
{
    if (NULL == a_unsorted || n <= 0)
    {
        cout<<"invalid input!"<<endl;
        exit(0);
    }

    return _bsearch_recursive(a_unsorted,0,n - 1,x);
}

//非递归implementation
int _bsearch_2(const int a_unsorted[],size_t n,int x)
{
    if (NULL == a_unsorted || n <= 0)
    {
        cout<<"invalid input!"<<endl;
        exit(0);
    }

    int begin = 0;
    int end = n - 1;
    int mid = 0;

    while (begin <= end)
    {
        mid = (begin + end)/2;

        if (x == a_unsorted[mid])
        {
            return mid;
        }

        /*    if (begin == end)   //不需要，在下一次循环中会因为不满足begin <= end而结束循环，返回-1
        {
        return -1;
        }
        */
        if (x < a_unsorted[mid])
        {
            end = mid - 1;
        }

        begin = mid + 1;
    }

    return -1;
}

//测试程序，即“脚手架”
int main()
{
    //int a_unsorted[SIZE] = {12,15,23,38,    48,49,52,67,    71,78,100};
    int a_unsorted[SIZE] = {12,15};
    int n = 2;
    int x;
    int pos;

    //test _bsearch_2
    cout<<"test _bsearch_1..."<<endl;
    cout<<"please enter the number to find : "<<endl;
    while (cin>>x)
    {
        cout<<"searching "<<x<<endl;
        pos = _bsearch_1(a_unsorted,n,x);
        if ( pos == -1)
        {
            cout<<x<<" is not found!"<<endl;
        }
        else
        {
            cout<<a_unsorted[pos]<<" is found"<<endl;
        }

        cout<<"please enter the number to find : "<<endl;
    }

    cin.clear();
    cin.sync();
    cout<<endl;

    //test _bsearch_2
    cout<<"test _bsearch_2..."<<endl;
    cout<<"please enter the number to find : "<<endl;
    while (cin>>x)
    {
        cout<<"searching "<<x<<endl;
        pos = _bsearch_2(a_unsorted,n,x);
        if ( pos == -1)
        {
            cout<<x<<" is not found!"<<endl;
        }
        else
        {
            cout<<a_unsorted[pos]<<" is found"<<endl;
        }

        cout<<"please enter the number to find : "<<endl;
    }

    return 0;
}

测试结果：

test _bsearch_1...
please enter the number to find :
12
searching 12
12 is found
please enter the number to find :
15
searching 15
15 is found
please enter the number to find :
11
searching 11
11 is not found!
please enter the number to find :
13
searching 13
13 is not found!
please enter the number to find :
18
searching 18
18 is not found!
please enter the number to find :
^Z

test _bsearch_2...
please enter the number to find :
12
searching 12
12 is found
please enter the number to find :
15
searching 15
15 is found
please enter the number to find :
11
searching 11
11 is not found!
please enter the number to find :
17
searching 17
17 is not found!
please enter the number to find :
13
searching 13
13 is not found!
please enter the number to find :
^Z
请按任意键继续. . .