This works correct even with 1000 numbers. (What else compilator wants? ))

#include <stdio.h>
int nod(int a, int b){
    while (a != 0 && b != 0){
        if (a > b)
            a = a % b;
        else
            b = b % a;
    }
    return a+b;
}
int main(){
    int size;
    int result = 1;
    scanf_s("%i", &size);
    int arr[1001];
    bool mask[1001];
    for (int i = 0; i < size; ++i)
        scanf_s("%i", &arr[i]);
    for (int i = 0; i < size; ++i){
        int k = 1, temp = arr[i];
        while (temp != i + 1){
            temp = arr[temp - 1];
            ++k;
        }
        if (mask[k] != false){
            mask[k] = false;
        result =result/nod(result,k) * k;

        }
    }
    printf("%i", result);
}

I tried to repair your code
[code deleted]

Edited by moderator 04.12.2019 20:38