[20250630] BOJ / G4 / 사이클 게임 / 이강현

Author: lkhyun

lkhyun/202506/30 BOJ G4 사이클 게임.md

@@ -0,0 +1,58 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main{
+    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 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());
+
+        parent = new int[n];
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+        }
+
+        int ans = 0;
+        for (int i = 1; i <= m; i++) {
+            st = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+            if(union(a,b)){
+                ans = i;
+                break;
+            }
+        }
+        bw.write(ans+"");
+        bw.close();
+    }
+    static int find(int cur){
+        if(cur == parent[cur]){
+            return cur;
+        }else{
+            return parent[cur] = find(parent[cur]);
+        }
+    }
+    static boolean union(int a, int b){
+        int rootA = find(a);
+        int rootB = find(b);
+
+        if(rootA == rootB){
+            return true;
+        }else{
+            if(rootA < rootB){
+                parent[rootA] = rootB;
+            }else{
+                parent[rootB] = rootA;
+            }
+            return false;
+        }
+    }
+}
+```