[20250319] BOJ / G4 / 도시 분할 계획 / 김수연

Author: suyeun84

suyeun84/202503/19 BOJ G4 도시 분할 계획.md

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+```java
+import java.io.*;
+import java.util.*;
+
+public class boj1647 {
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static StringTokenizer st;
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	
+	static int N, M;
+	static ArrayList<Node> roads;
+	static int[] parent;
+	
+	public static void main(String[] args) throws Exception {
+		nextLine();
+		N = nextInt();
+		M = nextInt();
+		int a, b, c, answer = 0;
+		roads = new ArrayList<>();
+		parent = new int[N+1];
+		for (int i = 0; i < N+1; i++) parent[i] = i;
+		for (int i = 0; i < M; i++) {
+			nextLine();
+			a = nextInt();
+			b = nextInt();
+			c = nextInt();
+			roads.add(new Node(a,b,c));
+		}
+		
+		roads.sort((o1, o2) -> o1.c-o2.c);
+		
+		int cnt = 0;
+		for (Node road : roads) {
+			if (cnt == N-2) break;
+			if (find(road.a) != find(road.b)) {
+				union(road.a, road.b);
+				answer += road.c;
+				cnt++;
+			}
+		}
+		System.out.println(answer);
+	}
+	
+	static void union(int a, int b) {
+		int A = find(a);
+		int B = find(b);
+		if (A==B) return;
+		if (A<B) parent[B] = A;
+		else parent[A] = B;
+	}
+	
+	static int find(int node) {
+		if (parent[node] == node) return node;
+		return parent[node] = find(parent[node]);
+	}
+	
+	static class Node{
+		int a, b, c;
+		public Node(int a, int b, int c) {
+			this.a = a;
+			this.b = b;
+			this.c = c;
+		}
+	}
+}
+
+```