[백준 9095, Java] 1,2,3 더하기

문제

www.acmicpc.net/problem/9095

9095번: 1, 2, 3 더하기

코드

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

public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int T = Integer.parseInt(br.readLine());
        for(int i=0;i<T;i++){
            int n = Integer.parseInt(br.readLine());
            count =0;
            countSum(n,0);
            bw.write(count+"\n");
        }
        bw.flush();
        br.close();
        bw.close();
    }
    static int count=0;
    static void countSum(int n,int sum){
        if(sum==n){
            count++;
        }
        else if(sum>n){
            return;
        }
        else{
            countSum(n,sum+1);
            countSum(n,sum+2);
            countSum(n,sum+3);
        }
    }

}

 

review

1. 경우의 수 문제는 순서 or 선택

  - 123 을 뽑을 때 123이랑 321이 다르다면 순서, 123이랑 321이 같다면 선택

2. NM2 문제 복습