求两个字符串的最大公共字串

//今天面试遇到一个有趣的题目 取两个字符串的最大公共字符串

//解决方案如下：



#include <stdio.h>

#include <stdlib.h>

#include <string.h>



//先造一个常用函数

char* strsub( char const* pStrSrc, int iStart, int iLen )

{

	if( !pStrSrc || iStart <  0 )

		return NULL;



	int iStrLen = strlen( pStrSrc );



	char* pStrRes = NULL;

	if( iLen >= iStrLen - iStart )

	{

		pStrRes = (char*)malloc( iStrLen - iStart + 1 );



		if( !pStrRes )

			return NULL;



		memset( pStrRes, 0,  iStrLen - iStart + 1 );



		strncpy( pStrRes, pStrSrc + iStart, iStrLen  - iStart );



		return pStrRes;

	}

	else

	{

		pStrRes = (char*)malloc( iLen + 1 );

		

		if( !pStrRes )

			return NULL;



		memset( pStrRes, 0, iLen + 1 );



		strncpy( pStrRes, pStrSrc + iStart, iLen );



		return pStrRes;



	}



}



char* maxComm( char* pStrLeft, char* pStrRight )

{

	if( !pStrLeft || !pStrRight )

	{

		return NULL;

	}



	char* pStrLess = NULL;

	char* pStrMore = NULL;

	char* pStrRes= NULL;



	int iLeft = strlen( pStrLeft );

	int iRight = strlen( pStrRight );



	int iLess = ( iLeft <= iRight ) ? iLeft : iRight;



	int i,j;

	

	if( iLeft <= iRight )

	{

		pStrLess = pStrLeft;

		pStrMore = pStrRight;

	}

	else

	{

		pStrLess = pStrRight;

		pStrMore = pStrLeft;

	}

	char* pSt = NULL;



	for( i = iLess; i > 0; i-- )

	{

		for( j = 0; j <= iLess - i; j++ )

		{

			pStrRes = strsub( pStrLess, j, i );



			if( strstr( pStrMore, pStrRes ) )

				return pStrRes;



			free( pStrRes );

			pStrRes = NULL;

		}

	}



	return NULL;

}



int main( int argc, char** argv )

{

	char* pStrLeft = "adasdfabc";

	char* pStrRight = "asdabcasdf";



	puts( "max comm string between two strings" );

	char* strMaxComm = maxComm( pStrLeft, pStrRight );

	printf( strMaxComm );

	puts( "" );



	free( strMaxComm );

	strMaxComm = NULL;



	return 0;

}