strchr(),strstr()函数实现

#include <iostream>
using namespace std;
char* my_strchr(char* str, int i)
{
if (NULL == str){
return NULL;
}

while('\0'!= *str && (char)i != *str){
++str;
}

if ((char)i == *str){
return (char*)str;
}

return NULL;
}

char* my_strstr(char* sr, const char* dest)
{
if (NULL == sr || NULL == dest){
return NULL;
}

while('\0' != *sr)
{
const char* str_str = sr;
const char* temp_dest = dest;
while('\0' != *temp_dest)
{
if (*temp_dest != *str_str)
break;
if ('\0' == *(++temp_dest))
return (char*)sr;
if ('\0' == *(++str_str))
return NULL;
}
++sr;
}

return NULL;
}

void main()
{
char* sr = "ABCDEF";
char* dest = "EF";
char* result = my_strstr(sr, dest);
const char* str = my_strchr(dest, int('C'));
if (NULL != str){
std::cout<<*str<<std::endl;
}
}