C高级day4

改写strlen  strcpy  strcmp   strcat。封装成函数

#include <stdio.h>                               

void strcpy1(char *,char *);
int strlen1(char *);
int strcmp1(char *,char *);
void strcat1(char *,char *);

int main(int argc,const char* argv[])
{
    char s1[30];
    char s2[10] = "abcdef";

    strcpy1(s1,s2);
    printf("%s\n",s1);


    char s3[20] = "abcdefgh";
    printf("%d\n",strlen1(s2));
    printf("%d\n",strcmp1(s3,s2));

    strcat1(s2,s3);
    printf("%s\n",s2);
      return 0;
}


void strcpy1(char *s1,char *s2)
{
    while(1)
    {
        *s1++ = *s2++;
        if(*(s2-1) == '\0')
            break;
    }

}

int strlen1(char *s)
{
    int count=0;
    while(*s++)
        count++;
    return count;
}

int strcmp1(char *s1,char *s2)
{
    while(*s1 != '\0' && *s1 == *s2)
    {
        s1++;
        s2++;
    }

    return *s1-*s2;

}

void strcat1(char *s1,char *s2)
{
    while(*s1)
        s1++;
    while(1)
    {
        *s1++ = *s2++;
        if(*(s2-1) == '\0')
            break;
    }

                                        
}