strchr(),strstr()函數實作

#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;
   }
}