删除字符串中重复字符

 char *delete_adjacent_char1(char *str)
...{
    if(str==NULL)
        return NULL;

    int i=0,j=0;
    int len=strlen(str);
    for(j=i+1;j<len;j++)
    ...{
        if(str[i]!=str[j])
            str[++i]=str[j];
    }
    str[i+1]=0;

    return str;
}

//2,3相同,只不过一个用while一个用for
char *delete_adjacent_char2(char *str)
...{
    if(str==NULL)
        return NULL;

    char *p=str;
    char *q=p+1;
    while(*q)
    ...{
        if(*p!=*q)
        ...{
            p++;
            *p=*q;
            q++;
        }
        else
        ...{
            q++;
        }
    }
    *(p+1)=0;
    
    return str;
}

//用for代码简洁
char *delete_adjacent_char3(char *str)
...{
    if(str==NULL)
        return NULL;

    char *p=str;
    char *q=p+1;
    for(;*q;q++)
    ...{
        if(*p!=*q)
        ...{
            p++;
            *p=*q;
        }        
    }
    *(p+1)=0;

    return str;
}