#include<conio.h>
#include<string.h>
#include<stdio.h>
int strlen1(char *str) {//用指標來接收陣列
int num = 0;//計數器
while (*str) {//*str!=’\0’
num++;
str++;//指標向後遍歷為’\0’跳出
}
return num;//返回字串長度
}
int strlen2(const char *str) {
const char *p = str;
while (*p++);//如果值不為0就++
return (int)(p - str - 1);
}
int strlen3(const char *str) {
if (str == NULL || *str == ‘\0’)
return 0;
return 1 + strlen3(str+1);
}
int strlen4(const char *str) {
return (str == NULL || *str == ‘\0’) ? 0 : 1 + strlen4(str+1);
}
int strlen5(const char *str) {
const char *p = str;
while (*p)//如果值不為0就++
p++;
return (int)(p - str);
}
int main()
{
char str[] = “hello world”;//陣列又是常數指標char const *str
printf(“string’s long :%d\n”,strlen(str));
printf(“string’s long :%d\n”, strlen1(str));
printf(“string’s long :%d\n”, strlen2(str));
printf(“string’s long :%d\n”, strlen3(str));
printf(“string’s long :%d\n”, strlen4(str));
printf(“string’s long :%d\n”, strlen5(str));
return 0;
}