[20251029] PGM / LV2 / 전력망을 둘로 나누기 / 강신지

Author: ksinji

ksinji/202510/29 PGM 전력망을 둘로 나누기.md

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+```java
+import java.util.*;
+
+class Solution {
+    public int solution(int n, int[][] wires) {
+        List<List<Integer>> g = new ArrayList<>();
+        for (int i = 0; i <= n; i++) g.add(new ArrayList<>());
+
+        for (int[] w : wires) {
+            g.get(w[0]).add(w[1]);
+            g.get(w[1]).add(w[0]);
+        }
+
+        int answer = Integer.MAX_VALUE;
+
+        for (int[] cut : wires) {
+            int a = cut[0];
+            int b = cut[1];
+
+            int sizeA = bfsCount(n, g, a, b);
+            int sizeB = n - sizeA;
+            int diff = Math.abs(sizeA - sizeB);
+
+            if (diff < answer) answer = diff;
+        }
+
+        return answer;
+    }
+
+    private int bfsCount(int n, List<List<Integer>> g, int a, int b) {
+        boolean[] visited = new boolean[n + 1];
+        Queue<Integer> q = new LinkedList<>();
+        q.add(a);
+        visited[a] = true;
+
+        int cnt = 0;
+
+        while (!q.isEmpty()) {
+            int cur = q.poll();
+            cnt++;
+
+            for (int nxt : g.get(cur)) {
+                if (isCutEdge(cur, nxt, a, b)) continue;
+                if (!visited[nxt]) {
+                    visited[nxt] = true;
+                    q.add(nxt);
+                }
+            }
+        }
+        return cnt;
+    }
+
+    private boolean isCutEdge(int u, int v, int a, int b) {
+        return (u == a && v == b) || (u == b && v == a);
+    }
+}
+
+```