指针字符串长度

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
void main()
{
    char *f;
    f = (char*)malloc(50);
    int n;
    scanf("%s", f);
    for (n = 0; *f != '\0'; f++)
        n++;
    printf("%d", n);
    f = f - n;
    free(f);
    //第二种方法
    char*p1, *p2;
    p1 = p2 = (char*)malloc(100);
    scanf("%s", p1);
    while (*p2!='\0')
    {
        p2++;    
    }
    printf("%d", p2 - p1);
    free(p1);
    getchar();
    getchar();
}