[20251027] BOJ / G5 / 숫자고르기 / 이종환

0224LJH/202510/27 BOJ 숫자고르기.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.PriorityQueue;
+import java.util.StringTokenizer;
+
+public class Main {
+	static StringBuilder sb = new StringBuilder();
+	static int totalNum,left;
+	static int[] arr,numCnt;
+	static boolean[] isDead;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        process();
+        print();
+    }
+
+    private static void init() throws IOException{
+    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    	totalNum = Integer.parseInt(br.readLine());
+    	left= totalNum;
+    	arr = new int[totalNum+1];
+    	numCnt = new int[totalNum+1];
+    	isDead = new boolean[totalNum+1];
+
+    	for (int i = 1; i <= totalNum; i++) {
+    		arr[i] = Integer.parseInt(br.readLine());
+    		numCnt[arr[i]]++;
+    	}
+    }
+
+    private static void process() {
+    	boolean isEnd = false;
+    	while(!isEnd) {
+    		isEnd = true;
+    		for (int i = 1; i <= totalNum; i++) {
+    			if (isDead[i]) continue;
+    			if (numCnt[i] == 0) {
+    				numCnt[arr[i]]--;
+    				isEnd = false;
+    				left--;
+    				isDead[i] = true;
+    			}
+    		}
+    	}
+
+    	sb.append(left);
+    	for (int i = 1; i<= totalNum; i++) {
+    		if(!isDead[i]) sb.append("\n").append(i);
+    	}
+
+    }
+
+
+
+    private static void print() {
+    	System.out.println(sb.toString());
+    }
+}
+
+
+```