[BOJ] 최소 스패닝 틔 / 골드4

Author: 최재익

jaeik/최소스패닝트리/BOJ_1197.java

@@ -0,0 +1,91 @@
+package 최소스패닝트리;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.Comparator;
+import java.util.PriorityQueue;
+import java.util.StringTokenizer;
+
+public class BOJ_1197 {
+    static class Edge implements Comparable<Edge> {
+        int start;
+        int end;
+        int weight;
+
+        public Edge(int start, int end, int weight){
+            this.start = start;
+            this.end = end;
+            this.weight = weight;
+        }
+
+        @Override
+        public int compareTo(Edge o) {
+            return this.weight-o.weight;
+        }
+    }
+
+    static int v, e;
+    static int[] parent;
+    static int[] rank;
+    static PriorityQueue<Edge> edges;
+    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());
+        e = Integer.parseInt(st.nextToken());
+
+        parent = new int[v+1];
+        rank = new int[v+1];
+        edges = new PriorityQueue<>();
+
+        for(int i=1; i<=v; i++){
+            parent[i] = i;
+        }
+
+        for(int i=0; i<e; i++){
+             st = new StringTokenizer(br.readLine());
+             int start = Integer.parseInt(st.nextToken());
+             int end = Integer.parseInt(st.nextToken());
+             int weight = Integer.parseInt(st.nextToken());
+
+            edges.add(new Edge(start, end, weight));
+        }
+
+        int sum = 0;
+        while(!edges.isEmpty()){
+            Edge edge = edges.poll();
+
+            if(find(edge.start)==find(edge.end))continue;
+
+            union(edge.start, edge.end);
+            sum += edge.weight;
+        }
+
+        System.out.println(sum);
+    }
+
+    static int find(int x){
+        if(parent[x]==x)return x;
+        return parent[x]=find(parent[x]);
+    }
+
+    static void union(int x, int y){
+        x = find(x);
+        y = find(y);
+
+        if(x==y)return;
+
+        if(rank[x]<rank[y]){
+            parent[x] = y;
+        }
+        else{
+            parent[y] = x;
+
+            if(rank[x]==rank[y]){
+                rank[x]++;
+            }
+        }
+    }
+}