字符串复制，求长度，求子串

#include<iostream>#include<string>              //头文件#include<assert.h>            //assert的头文件using namespace std;char *strcpy1( char *strDest, const char *strSrc)             //复制字符串{    if( (strDest==NULL)||(strSrc==NULL) ){return NULL;}char *strDestCopy = strDest;while((*strDest++=*strSrc++)!='\0');return strDestCopy;}int strlen1( const char *src)                                  //求子长{assert(NULL!=src);int len = 0;while(*src++!='\0')len++;return len;}int strlen2( const char *src)                                  //求子长{assert(NULL!=src);const char *temp=src;while(*src++!='\0');return (src-temp-1);}const char* strstr1( const char *src, const char *sub)          //求子串{   const char *bp;   const char *sp;   if( src==NULL || NULL == sub)   {   return src;   }   while(*src)   {   bp=src;   sp=sub;   do{    if(!*sp) return src;   }while( *bp++==*sp++);   src+=1;   }   return NULL;}int main(){    char *strDest = new char[4];    char *strSrc = "123";strcpy1(strDest, strSrc);cout<<strDest<<endl;cout<<strlen1(strDest)<<endl;cout<<strlen2(strDest)<<endl;cout<<strstr(strSrc,"1")<<endl;return 0;}