Create 1197_최소 스패닝 트리.java

1197_최소 스패닝 트리.java

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+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.PriorityQueue;
+import java.util.StringTokenizer;
+
+public class Main {
+
+	static class Edge implements Comparable<Edge>{
+		int from, to;
+		int weight;
+
+		public Edge(int from, int to, int weight) {
+			super();
+			this.from = from;
+			this.to = to;
+			this.weight = weight;
+		}
+		@Override
+		public int compareTo(Edge o) {
+			return Integer.compare(this.weight, o.weight);
+		}
+	}
+
+	static int V, E;
+	static int[] parents;
+
+	static void make() { //초기화 메서드
+		parents = new int[V];
+		for (int i = 0; i < V; i++) {
+			parents[i] = i;
+		}
+	}
+
+	static int find(int a) { //root노드 찾아주는 메서드
+		if(parents[a] == a) return a;
+		return parents[a] = find(parents[a]);
+	}
+
+	static boolean union(int a, int b) { //b의 root 변경 메서드
+		int aRoot = find(a);
+		int bRoot = find(b);
+		if(aRoot == bRoot) return false;
+		parents[bRoot] = aRoot;
+		return true;
+	}
+
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine()," ");
+
+		V = Integer.parseInt(st.nextToken()) + 1; //정점 1부터 시작
+		E = Integer.parseInt(st.nextToken());
+
+		PriorityQueue<Edge> pq = new PriorityQueue<>(); //우선순위 큐 사용
+
+		for(int i=0; i<E; i++) { //간선 및 가중치 입력
+			st = new StringTokenizer(br.readLine()," ");
+			int from = Integer.parseInt(st.nextToken());
+			int to = Integer.parseInt(st.nextToken());
+			int weight = Integer.parseInt(st.nextToken());
+			pq.add(new Edge(from, to, weight));
+		}
+
+		//V개의 정점으로 make set 작업
+		make();
+
+		int result = 0; //MST 비용
+		int cnt = 0; //연결된 간선 개수
+
+		for(int i=0; i<pq.size(); i++) {
+			Edge e = pq.poll();
+			if(union(e.from, e.to)) { //사이클 형성 확인
+				result += e.weight; //값 합산
+				if(++cnt == V-1) break; //스패닝 트리 완성조건
+			}
+			i--;
+		}
+		System.out.println(result);
+	}
+}