From 6ad7a91defff484f79bff7da653baf8a6b9e07c3 Mon Sep 17 00:00:00 2001
From: oncsr <khj20006@naver.com>
Date: Thu, 18 Dec 2025 23:48:36 +0900
Subject: [PATCH] =?UTF-8?q?[20251218]=20BOJ=20/=20P5=20/=20Lights=20/=20?=
 =?UTF-8?q?=EA=B6=8C=ED=98=81=EC=A4=80?=
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---
 khj20006/202512/18 BOJ P5 Lights.md | 85 +++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 khj20006/202512/18 BOJ P5 Lights.md

diff --git a/khj20006/202512/18 BOJ P5 Lights.md b/khj20006/202512/18 BOJ P5 Lights.md
new file mode 100644
index 00000000..2912404c
--- /dev/null
+++ b/khj20006/202512/18 BOJ P5 Lights.md	
@@ -0,0 +1,85 @@
+```java
+import java.sql.Array;
+import java.util.*;
+import java.io.*;
+
+public class Main {
+
+    static BufferedReader br;
+    static BufferedWriter bw;
+    static StringTokenizer st;
+
+    static int N, M;
+    static long[] toggle;
+    static List<long[]> results;
+    static List<long[]> leftResults;
+    static Map<Long, Integer> rightResults;
+
+    public static void main(String[] args) throws Exception {
+
+        input();
+        solve();
+
+    }
+
+    public static void input() throws Exception {
+        br = new BufferedReader(new InputStreamReader(System.in));
+
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        toggle = new long[N];
+        for(int i=0;i<N;i++) toggle[i] = (1L<<i);
+        for(int i=0;i<M;i++) {
+            st = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(st.nextToken()) - 1;
+            int b = Integer.parseInt(st.nextToken()) - 1;
+            toggle[a] |= (1L<<b);
+            toggle[b] |= (1L<<a);
+        }
+
+        br.close();
+    }
+
+    public static void solve() throws Exception {
+        bw = new BufferedWriter(new OutputStreamWriter(System.out));
+
+        results = new ArrayList<>();
+        bck(0, N/2, 0, 0);
+        leftResults = new ArrayList<>();
+        leftResults.addAll(results);
+
+        results = new ArrayList<>();
+        bck(N/2, N, 0, 0);
+        rightResults = new TreeMap<>();
+        for(long[] info : results) {
+            long status = info[0];
+            int cnt = (int)info[1];
+            if(!rightResults.containsKey(status) || rightResults.get(status) > cnt) rightResults.put(status, cnt);
+        }
+
+        long ans = N;
+        for(long[] info : leftResults) {
+            long leftStatus = info[0];
+            int cntLeft = (int)info[1];
+            long target = ((1L<<N)-1) ^ leftStatus;
+            int cntRight = rightResults.getOrDefault(target, 12345);
+            ans = Math.min(ans, cntLeft + cntRight);
+        }
+
+        bw.write(ans + "\n");
+
+        bw.close();
+    }
+
+    public static void bck(int pos, int tar, int cnt, long status) {
+        if(pos == tar) {
+            results.add(new long[]{status,cnt});
+            return;
+        }
+        bck(pos+1, tar, cnt, status);
+        bck(pos+1, tar, cnt+1, status ^ toggle[pos]);
+    }
+
+}
+```