License Plate

license_plate.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int check1(char *s) {
    return strlen(s) == 1;
}

int check2(char *s) {
    char *p = s;
    while((*p == *s)) {
        p++;
    }
    if (*p == '\0')
        return 1;
    return 0;
}

int check3(char *s) {
    char *p = s;
    if (strlen(s) >= 3) {
        while( (*(p+1) != '\0') && (*(p+1) == ((*p)+1))) {
            p++;
        }
        if (*(p+1) == '\0')
            return 1;
    }
    return 0;
}

int check4(char *s) {
    char *p,*q;
    if (strlen(s) >= 3) {
        p = s;
        q = &(s[strlen(s)-1]);
        while((p < q) && (*p == *q)) {
            p++;
            q--;
        }
        if (*p == *q) 
            return 1;
    }
    return 0;
}

int check5(char *s) {
    int n;
    n = atoi(s);
    return (n % 100) == 0;
}

int check6(char *s) {
    char *p,*q;
    if (strlen(s) == 4) {
        p = s;
        q = s+2;
        while((*q != '\0') && (*p == *q)) {
            p++;
            q++;
        }
        if( *q == '\0')
            return 1;
    }
    return 0;
}
int main(int argc, char **argv) {
    char in[5];
    in[0] = ' ';
    in[1] = '\0';
    scanf("%s",in);
    while(strcmp(in,"-1")) {
        if (check1(in) || check2(in) || check3(in) || check4(in) || check5(in) || check6(in))
            printf("%s\n",in);
        scanf("%s",in);
    }
    return 0;
}