/*字符串升序快排 每个字母都比较*/
int cmp(const void* a, const void* b){
    char* s1 = *(char**)a;
    char* s2 = *(char**)b;
    while(*s1 == *s2 && *s1 && *s2) 
        s1++,s2++;
    return *s1 - *s2;
}