一。循环实现

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int my_strlen(char *pstr)
{int num = 0;while (*pstr != '\0'){num++;pstr++;}return num;
}
int main()
{int count = 0;char str[100] = { 0 };printf("请输入一个字符串");scanf("%s", str);count=my_strlen(str);printf("%d\n", count);return 0;
}

二。递归实现

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int my_strlen(char* pstr)
{if (*pstr != '\0')return 1 + my_strlen(pstr + 1);elsereturn 0;}
int main()
{int count = 0;char str[100] = { 0 };printf("请输入一个字符串");scanf("%s", str);count = my_strlen(str);printf("%d\n", count);return 0;
}