백준 9506번 약수들의 합 문제
백준 9506번 자바 약수들의 합 풀이
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class Main {
public static void main(String[] args) throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
while (true) {
int n = Integer.parseInt(br.readLine());
if (n == -1) {
break;
}
ArrayList<Integer> divisorList = divisorList(n);
int sum = 0;
String plusStr = "";
for (int divisorNum : divisorList) {
if (divisorNum != divisorList.get(divisorList.size() - 1)) {
sum = sum + divisorNum;
plusStr += divisorNum == 1 ? "" + divisorNum : " + " + divisorNum;
}
}
if (sum == divisorList.get(divisorList.size() - 1)) {
sb = sb.append(n).append(" = ").append(plusStr).append("\n");
} else {
sb = sb.append(n).append(" is NOT perfect.").append("\n");
}
}
System.out.println(sb);
}
public static ArrayList<Integer> divisorList(int num) {
ArrayList<Integer> divisorList = new ArrayList<Integer>();
int sqrt = (int) Math.sqrt(num);
for (int i = 1; i <= sqrt; i++) {
if (num % i == 0) {
divisorList.add(i);
if (num / i != i) {
divisorList.add(num / i);
}
}
}
divisorList.sort(Comparator.naturalOrder());
return divisorList;
}
}
