main.c

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

/* This function should return 1 if x is prime and 0 otherwise */
int isPrime(int x){
    if(x <= 1) return 0;
    for(int i = 2; i <= sqrt(x); i++){
        if(x % i == 0) return 0;
    }
    return 1;
}


/* This function should return 1 if gcd(x,2)=1 and 0 otherwise */
int isGcd1(int x){
    int a = x;
    int b = 2;
    int r;

    while (b != 0) {
        r = a % b;
        a = b;
        b = r;
    }
    if(a == 1) {
        return 1;
    }else{return 0;}
}

/* This function should return 1 if 9^x-2 mod 5 = 2 and 0 otherwise */
int is2mod5(int x){
    if (x % 2 == 0){return 0;}
    else {return 1;}
}


int main(void){
    int x;
    int p, q, r;

    printf("What number do you want to test?\n");
    scanf("%d", &x);
    printf("x is %d\n", x);

    p = isPrime(x);
    q = isGcd1(x);
    r = is2mod5(x);

    if ((p && !r) || (!p && q &&!r) || (!p && !q && r)){
        printf("You have found a valid x\n");
        printf("p is %d, q is %d, and r is %d\n", p,q,r);
    } else {
        printf("p is %d, q is %d, and r is %d\n", p,q,r);
        printf("Try again!\n");
    }

    return EXIT_SUCCESS;
}