[Java]프로그래머스 Lv. 0 구슬을 나누는 경우의 수

https://school.programmers.co.kr/learn/courses/30/lessons/120840

프로그래머스

나의 풀이

class Solution {
    public int solution(int balls, int share) {
        return combination(balls, share);
    }

    public static int combination(int balls, int share) {
        if (balls == share || share == 0) return 1;
        return combination((balls - 1), (share - 1)) + combination(balls - 1, share);
    }
}

다른 풀이

import java.math.BigInteger;

class Solution {
    public BigInteger solution(int balls, int share) {
        return factorial(balls).divide(factorial(balls - share).multiply(factorial(share)));
    }

    public BigInteger factorial(int n) {
        BigInteger result = new BigInteger("1");
        BigInteger from = new BigInteger("1");
        BigInteger to = new BigInteger(String.valueOf(n));

        for (BigInteger i = from; i.compareTo(to) <= 0; i = i.add(BigInteger.ONE)) {
            result = result.multiply(i);
        }
        return result;
    }
}

class Solution {
    public long solution(int balls, int share) {
        share = Math.min(balls - share, share);

        if (share == 0)
            return 1;

        long result = solution(balls - 1, share - 1);
        result *= balls;
        result /= share;

        return result;
    }
}