[BOJ/백준][Silver2] 2407 : 조합 (Kotlin)

https://www.acmicpc.net/problem/2407

2407번: 조합

 

[난이도] Silver2
[유형] 수학

[풀이]
nCm 공식을 적용하여 분자, 분모를 각각 계산한 뒤 분자/분모를 해준것이 정답입니다.
n,m이 100 제한이라 unsigned long 범위도 넘어가므로 BigInteger를 이용해야 합니다.
C++같이 BigInteger를 지원하지 않는 경우에는 String을 통한 덧셈 연산으로 해결해야 합니다.

 

import java.io.BufferedReader
import java.io.InputStreamReader
import java.math.BigInteger
import java.util.*

fun main() = with(BufferedReader(InputStreamReader(System.`in`))){
    val (N,M) = readLine().split(' ').map{it.toInt()}
    var up = BigInteger("1")
    var down = BigInteger("1")
    for(i in 1..M){
        up = up.multiply(BigInteger((N-i+1).toString()))
        down = down.multiply(BigInteger(i.toString()))
    }
    println(up.divide(down))
}

https://github.com/has2/Problem-Solving/blob/master/boj-solved.ac/Silver2/2407.cpp