strlen实现:

int my_strlen(char *str)
{
    char *tmp = str;
    while (*str)
    {
        str++;
    }
    return str - tmp;

字符串遍历:

 

void stringDis(char *str)
{
    //int len = sizeof(str) / sizeof(char); //error if there is space
    //int len = strlen(str);    //<string.h>
    int len = my_strlen(str); //same as strlen()
    for (int i = 0; i < len;i++)
    {
        printf("%c", str[i]);
    }
    printf("\n");
}