SPOJ Problem CRZYSMKR

CRAZY SMOKER

Explanation:

A simple problem which requires li'l bit of modular arithmetics and we are done.
We just need to calculate the results of (34 ^ n) % 11 and (30 * n) % 11. Add 32 to it.

Once we have the result of above calculation, we need to find the minimum number to be added to the above result so that final result becomes equal to (0 % 11). We do it by subtracting it from 11 and taking a modulo 11. Taking modulo 11 helps for the case where n = 0.

Below is the code for reference.

Solution:

#include <iostream>
#include <cstdio>
using namespace std;

long long int mulMod(long long int a, long long int b, long long int c){
    // returns (a * b) % c.
    long long int x = 0, y = a % c;
    while (b) {
        if (b & 1)
            x = (x + y) % c;
        y = (y << 1) % c;
        b >>= 1;
    }
    return (x % c);
}

long long int modPower(long long int a, long long int b, long long int c){
    // returns (a ^ b) % c.
    long long int y = 1;
    while (b) {
        if (b & 1)
            // y = (y * a) % mod;
            y = mulMod(y, a, c);
        // a = (a * a) % mod;
        a = mulMod(a, a, c);
        b >>= 1;
    }
    return y;
}

long long int calculateCigarettes(long long int n){
    return (modPower(34, n, 11) + mulMod(30, n, 11) + 32) % 11;
}

int main() {
    int t;
    long long int n;
    scanf("%d", &t);
    while(t--){
        scanf("%lld", &n);
        printf("%lld\n", (11 - calculateCigarettes(n)) % 11);
    }
    return 0;
}

Any suggestions are welcome.