[20251128] BOJ / G4 / 전력난 / 이인희

LiiNi-coder/202511/28 BOJ 전력난.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main{
+	private static int M;
+	private static int N;
+	private static List<int[]> Edges;
+	private static int sumEdge;
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		String[] temp;
+		while(true){
+			temp = br.readLine().split(" ");
+			M = Integer.parseInt(temp[0]);
+			N = Integer.parseInt(temp[1] );
+			if(M == 0 && N == 0){
+				break;
+			}
+			Edges = new ArrayList<>();
+			sumEdge = 0;
+			int n = N;
+			while(n-->0){
+				temp = br.readLine().split(" ");
+				sumEdge += Integer.parseInt(temp[2]);
+				Edges.add(new int[]{
+					Integer.parseInt(temp[0]),
+					Integer.parseInt(temp[1]),
+					Integer.parseInt(temp[2])
+				});
+			}
+			solve();
+			System.out.println(sumEdge);
+		}
+	}
+
+	private static void solve() {
+		List<List<int[]>> graph = new ArrayList<>();
+		for(int i = 0; i < M; i++)
+			graph.add(new ArrayList<>());
+		for(int[] edge : Edges){
+			graph.get(edge[0]).add(new int[]{edge[1], edge[2]});
+			graph.get(edge[1]).add(new int[]{edge[0], edge[2]});
+		}
+		//프림
+		Queue<int[]> q = new PriorityQueue<>((o1, o2) -> o1[1] - o2[1]);
+		boolean[] visited = new boolean[M];
+		int visitedCount = 1;
+		visited[0] = true;
+		for(int[] next : graph.get(0)){
+			int nv = next[0];
+			int w = next[1];
+			q.offer(new int[]{nv, w});
+		}
+		while(visitedCount < M){
+			// -- 최소힙에서 팝
+			int[] temp = q.poll();
+			int nv = temp[0];
+			int w = temp[1];
+			// -- 만약 다음 정점번호가 방문이면 컨티뉴
+			if(visited[nv])
+				continue;
+			// 방문여부 표시
+			visited[nv] =true;
+			visitedCount++;
+			// -- 스패닝 트리 간선 처리
+			sumEdge -= w;
+			for(int[] next : graph.get(nv)){
+				int nnv = next[0];
+				if(visited[nnv])
+					continue;
+				int nw = next[1];
+				q.offer(new int[]{nnv, nw});
+			}
+			// -- 최소힙에 푸시
+		}
+	}
+}
+```