[JAVA] 단계별로 풀어보기 6. 함수

1. BOJ15596  정수 N개의 합

https://www.acmicpc.net/problem/15596

15596번: 정수 N개의 합

public class Test {
    long sum(int[] a) {
        long ans = 0;
        
        for(int i=0 ; i<a.length ; i++) {
            ans+=a[i];
        }
        return ans;
    }
}

java8

 

2. BOJ4673 Self Numbers

https://www.acmicpc.net/problem/4673

4673번: 셀프 넘버

import java.io.IOException;
import java.util.Arrays;

public class Main {
	public static void main(String[] args) throws IOException {
		boolean[] isSelfNumber = new boolean[10000];
		StringBuilder sb = new StringBuilder();

		for (int i = 1; i <= 10000; i++) {
			int n = d(i);
			if (n <= 10000)
				isSelfNumber[n - 1] = true;
		}

		for (int i = 0; i < 10000; i++) {
			if (!isSelfNumber[i])
				sb.append(i + 1).append('\n');
		}

		System.out.print(sb.toString().trim());

	}

	public static int d(int n) {
		int sum = n;

		while (n > 0) {
			sum += n % 10;
			n /= 10;
		}
		return sum;
	}
}

 

3. BOJ1065  한수

https://www.acmicpc.net/problem/1065

1065번: 한수

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	static int count = 0;

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());

		if (n < 100)
		    System.out.println(n);
		else {
			if (n == 1000)
				n = 999;
			count = 99;
			for (int i = 100; i <= n; i++)
				isSequence(i);
		System.out.println(count);
        }
	}

	public static void isSequence(int n) {
		int hun = n / 100;
		int ten = (n / 10) % 10;
		int one = n % 10;

		if ((hun - ten) == (ten - one)) {
			count++;
		}
	}
}