strlen实现

#include<assert.h>
#include<stdio.h>
int my_strlen(const char* strDest)
{
    assert(NULL!=strDest);
    if(‘\0‘==*strDest)
        return 0;
    else
        return(1+my_strlen(++strDest));
}

int my_strlen1(const char* strDest)
{
        assert(NULL!=strDest);
        return (‘\0‘!=*strDest)?(1+my_strlen(strDest+1)):0;
}

int my_strlen2(const char* strDest)
{
    if(strDest==NULL)
        return 0;
    int len=0;
    //for(;*strDest++!=‘\0‘;)
    while(*strDest++)
    {
        len++;
    }
    return len;
}

int my_strlen3(const char* strDest)
{
    assert(strDest);
    const char* p=strDest;
    while(*p++);
    return p-strDest-1;
}

int my_strlen4(const char* strDest)
{
    assert(strDest);
    const char *sc;
    for(sc=strDest;*sc!=‘\0‘;++sc);
    return sc-strDest;
}

int main()
{
    char* a="abcdefg";
    char* b="";
    char len,len1;
    len  = my_strlen4(a);
    len1 = my_strlen4(b);
    printf("len=%d,len1=%d\n",len,len1);
}