[BaekJoon] 27433번 팩토리얼 2 문제 풀이 (Success)

27433번: 팩토리얼 2

 

☕Language: Java

 

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
 
public class Main {
 
    public static void main(String[] args) throws IOException {
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
        int n = Integer.valueOf(br.readLine());
 
        long sum = 1;
        while (n-- > 0) {
            sum *= (n + 1);
        }
 
        bw.write(sum + "");
 
        bw.flush();
        bw.close();
 
    }
}
 

🤔 해설

1. sum *= (n + 1);

    - num--, 후위 연산자에 의해 n 값이 감소된 상태로 계산되므로 +1

 

😮 이 외의 풀이

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;
 
public class Main {
 
    public static void main(String[] args) throws IOException {
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
        StringTokenizer st = new StringTokenizer(br.readLine());
        long N = Long.valueOf(st.nextToken());
 
        bw.write(factorial(N) + "");
 
        bw.flush();
        bw.close();
 
    }
 
    public static long factorial(long N) {
 
        if (N <= 1)
            return 1;
 
        return N * factorial(N - 1);
    }
}
 

1. factorial(long N)

    - 재귀호출 사용

    - 매개변수 N에서 직접 계산하므로 처음부터 타입을 long으로 입력받음

 

 

 

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