求字符串长度的三种方法

1.指针

#include<stdio.h>

  
int strlen(char s[])

{

    int len=0;

	while(*s++!='\0')

	{

       len++;

	}

	return len;

}

int main()

{

	char s[]="123456789";

	printf("%d\n",strlen(s));

	system("pause");

   return 0;

}

  
  
2.计数

#include<stdio.h>

  
int strlen(char s[])

{

    int i=0;

	int count=0;

	while(s[i++]!='\0')

	{

     count++;

	}

	return count;

}

int main()

{

	char s[]="123456789";

	printf("%d\n",strlen(s));

	system("pause");

   return 0;

}

  
3.递归

#include<stdio.h>

  
int strlen(char s[])

{

  
   if(*s=='\0')

    return 0;

   else

    return 1+strlen(s+1);

}

int main()

{

	char s[]="abcdef";

	printf("%d\n",strlen(s));

	system("pause");

   return 0;

}