求兩個字符串的最大公共字串

//今天面試遇到一個有趣的題目 取兩個字符串的最大公共字符串
//解決方案如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//先造一個常用函數
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;
}