Happy Boy

#include <stdio.h>

int countDigits(int n) {
    int count = 0;
    while (n != 0) {
        n /= 10; ++count;
    }

    return count;
}

int happyNumber(int n) {
    // Return 1 if n is happy, 0 otherwise
    int digits = countDigits(n);
    int left = 0, right = 0, i;

    for (i = 0; i < digits / 2; ++i) {
        right += n % 10; n /= 10;
    }

    if (digits % 2 == 1) n /= 10;

    for (i = 0; i < digits / 2; ++i) {
        left += n % 10; n /= 10;
    }

    if (left == right) return 1;
    return 0;
}

int main()
{
    int n;
    printf("n = ");
    scanf("%d", &n);

    for (int i = 0; i < n; ++i)
        if (happyNumber(i * i)) printf("\n%d %d", i, i * i);

    return 0;
}