在指定字符串中查找第一次找到所查找的字符和最后一次查找的到的字符

<span style="font-family: Arial, Helvetica, sans-serif;">1：最后一次查找到字符</span></span>

#include<stdio.h>
char const *strrchr(char const *str,int ch)
{
char const *ret=NULL;
int n=0;
while(*str!='\0')
{
if(*str==ch)
{
ret=str;
str++;
n++;
}
else
str++;
}
if(0==n)
return NULL;
else
return ret;
}
void main()
{
char *str="hello e word";
int ch='w';
char const *ret=(char const *)strrchr(str,ch);
if(ret==NULL)
printf("返回值为:NULL\n");
else
printf("%c\n",*ret);
}

<span style="font-family: Arial, Helvetica, sans-serif;">2：第一次查找到字符</span>

#include<stdio.h>
char const *strchr(char const *str,int ch)
{
while(*str!='\0')
{
if(*str==ch)
return str;
else
str++;
}

return NULL;
}
void main()
{
char *str="hello word";
int ch='e';
char const *ret=(char const *)strchr(str,ch);
if(ret==NULL)
printf("返回值为:NULL\n");
else
printf("%c\n",*ret);
}