백준 11050번

원본 : www.acmicpc.net/problem/11050

11050번: 이항 계수 1

 

풀이

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class Main {

	public static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	public static BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));

	public static void main(String[] args) throws Exception {
		String str = reader.readLine();
		writer.write(fnBinomial(Integer.parseInt(str.split(" ")[0]), Integer.parseInt(str.split(" ")[1])) + "");
		writer.flush();
	}
	
	public static int factorial(int num) {
		if (num <= 1) {
			return 1;
		} else {
			return num * factorial(num - 1);
		}
	}
	
	public static int fnBinomial(int n, int r) {
		return factorial(n) / factorial(r) / factorial(n - r);
	}
	
}