Calculate different sequence of scores in a Volleyball match - https://www.hackerrank.com/contests/w1/challenges/volleyball-match

volley.php

#!/usr/bin/env php
<?php

const MOD = 1e9 + 7;

function fact($n) {
    return ($n > 1) ? $n * fact($n - 1) : 1;
}

function mpow($base, $exp, $mod) {
    $r = 1;
    for ($exp; $exp > 0; $exp--) {
        $r = $r * $base % $mod;
    }
    return $r;
}

function volley($a, $b) {
    list($a, $b) = $a > $b ? [$a, $b] : [$b, $a];

    if ($a < 25
        || ($a == 25 and ($a - $b) < 2)
        || ($a > 25 && ($a - $b) != 2)
    ) {
        return 0;
    }

    $exp = 0;
    $a -= 1;

    if ($a >= 25) {
        $exp = $b - 24;
        $a = $b = 24;
    }

    $c = floor(fact($a + $b) / (fact($a) * fact($b))) % MOD;
    return $c * mpow(2, $exp, MOD) % MOD;
}

// main:
$a = (int) trim(fgets(STDIN));
$b = (int) trim(fgets(STDIN));

echo volley($a, $b) . PHP_EOL;

volley.py

#!/usr/bin/env python3
from math import factorial

MOD = int(1e9 + 7);

def volley(a, b):
    a, b = (a, b) if a > b else (b, a)

    if a < 25 \
            or (a <= 25 and (a-b) < 2) \
            or (a > 25 and (a-b) != 2):
        return 0

    a -= 1
    exp = 0

    if a >= 25:
        exp = b - 24
        a = 24
        b = 24

    ans = factorial(a + b) // (factorial(a) * factorial(b)) % MOD
    return ans * pow(2, exp, MOD) % MOD


if __name__ == '__main__':
    a = int(input())
    b = int(input())

    print("%d" %volley(a, b))