[20250628] BOJ / G4 / 도시 분할 계획 / 이강현

lkhyun/202506/28 BOJ G4 도시 분할 계획.md

@@ -0,0 +1,79 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main{
+    static class Edge{
+        int u,v,weight;
+
+        Edge(int u,int v,int w){
+            this.u=u;
+            this.v=v;
+            this.weight=w;
+        }
+    }
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+    static int N,M;
+    static List<Edge> l;
+    static int[] parent;
+
+    public static void main(String[] args) throws Exception{
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        l = new ArrayList<>();
+        parent = new int[N+1];
+        for (int i = 1; i <= N; i++) {
+            parent[i] = i;
+        }
+
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int u = Integer.parseInt(st.nextToken());
+            int v = Integer.parseInt(st.nextToken());
+            int w = Integer.parseInt(st.nextToken());
+            l.add(new Edge(u,v,w));
+        }
+        l.sort((a, b) -> a.weight - b.weight);
+
+        int count = N-1;
+        int sum = 0;
+        for(Edge e:l){
+            if(merge(e.u,e.v)){
+                count--;
+                if(count==0){
+                    break;
+                }
+                sum += e.weight;
+            }
+        }
+        bw.write(sum+"\n");
+        bw.close();
+    }
+    static int find(int cur){
+        if(parent[cur]==cur){
+            return cur;
+        }else{
+            return parent[cur] = find(parent[cur]);
+        }
+    }
+    static boolean merge(int u, int v){
+        int uRoot = find(u);
+        int vRoot = find(v);
+
+        if(uRoot==vRoot){
+            return false;
+        }else{
+            if(uRoot<vRoot){
+                parent[vRoot] = uRoot;
+            }else{
+                parent[uRoot] = vRoot;
+            }
+            return true;
+        }
+    }
+}
+```