2.2

#include <stdio.h>
unsigned int strlength_b(const char *s) {
        const char *p=s;
        while (*++s);
        return s-p;
    }
unsigned int strlength_a(const char *s) {
        const char *p=s;
        while (*s++);
        return s-p;
    }
unsigned int strlength_c(const char *s) {
        const char *p=s;
        while (*s) s++;
        return s-p;
    }
int main (void) {
    char str[] = "\na\nd\n\0e\nh\n";
    printf("strlen_a = %u\n",strlength_a(str));//6
    printf("strlen_b = %u\n",strlength_b(str));//5
    printf("strlen_c = %u\n",strlength_c(str));//5
    printf("strlen = %1u\n",strlen(str));//5
    printf("sizeof = %1u\n",sizeof str);//11
return 0;
    }