C语言中strlen的几种写法

Num1: //用指针

int strlen(char *p){char *q = p;while(*q != '\0')   q++;retrun q - p;}

Num2: // 用指针

int strlen(char *p){int num;for(num = 0; *p != '\0'; p++)    num++;return num;}

Num3: //用数组方法，效率相对偏低

int strlen(char p[]){int i = 0;while(p[i] != '\0')    i++;return i;}