【字符串问题】返回一个字符串的指定子串

2013-09-15 11:06:57

模拟C++中的strstr函数，将主串中子串以及以后的字符串全部返回。

注意：

考虑所有可能的测试用例，包括子串存在、不存在，以及子串、主串为空的情况等。

---

 

代码（测试暂未发现问题，欢迎交流指正！）：

#include <iostream>
#include <cassert>
using namespace std;

char *MyStrstr(const char* pSrcStr,const char* pSubStr)
{
    assert(pSrcStr != NULL && pSubStr!= NULL);

    if (! *pSubStr )   //对子串为空的情况特别处理，否则在子串为空时返回原串
    {
        return NULL;
    }

    char *pSrcCur = (char *)pSrcStr;
    char *pSubCur = NULL;
    char *pSrcTmp = NULL;

    while (*pSrcCur)
    {
        pSrcTmp = pSrcCur;
        pSubCur = (char *)pSubStr;

        while (*pSrcTmp && *pSrcTmp == *pSubCur)
        {
            ++pSrcTmp;
            ++pSubCur;
        }

        if ( !(*pSubCur) )   //子串的所有字符都测试通过，说明找到子串，返回起始位置即可
        {
            return pSrcCur;
        }

        ++pSrcCur;
    }

    return NULL;   //没有找到，返回NULL
}

typedef char *  pCHAR;

void TestDriver()
{
    pCHAR srcStrArray[] = {"0123456","0123456","yyabcdabjcabceg","abcbcbcabc","abc","",""};
    pCHAR subStrArray[] = {"123","45678","abc","hello","","","abc"};
    size_t arrayLength = 7;

    pCHAR srcStr;
    pCHAR subStr;

    pCHAR pSubPos;
    
    for (size_t index = 0;index < arrayLength;++index)
    {
        srcStr = srcStrArray[index];
        subStr = subStrArray[index];
        pSubPos = MyStrstr(srcStr,subStr);

        cout<<"the source string is : "<<srcStr<<endl;
        cout<<"the sub string is : "<<subStr<<endl;

        if (pSubPos != NULL)
        {
            cout<<"the sub string is : "<<pSubPos<<endl<<endl;
        }
        else
        {
            cout<<"the sub string is not found!"<<endl<<endl;
        }
    }
}

int main()
{
    TestDriver();
    return 0;
}

测试结果：

the source string is : 0123456
the sub string is : 123
the sub string is : 123456

the source string is : 0123456
the sub string is : 45678
the sub string is not found!

the source string is : yyabcdabjcabceg
the sub string is : abc
the sub string is : abcdabjcabceg

the source string is : abcbcbcabc
the sub string is : hello
the sub string is not found!

the source string is : abc
the sub string is :
the sub string is not found!

the source string is :
the sub string is :
the sub string is not found!

the source string is :
the sub string is : abc
the sub string is not found!

请按任意键继续. . .