[20260312] BOJ / D4 / Internet Monopoly / 권혁준

Author: oncsr

khj20006/202603/12 BOJ D4 Internet Monopoly.md

@@ -0,0 +1,127 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class BOJ29851 {
+
+    static class Query {
+        int type, a, b;
+        Query(int a) {
+            this.type = 0;
+            this.a = a;
+        }
+        Query(int a, int b) {
+            this.type = 1;
+            this.a = a;
+            this.b = b;
+        }
+    }
+
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+
+    static int N, Q;
+    static Query[] queries;
+    static BitSet cantUnion;
+    static List<Integer>[] tree;
+    static int[] root, parent, depth;
+
+    public static int find(int x) {
+        return x == root[x] ? x : (root[x] = find(root[x]));
+    }
+
+    public static boolean union(int a, int b) {
+        int x = find(a), y = find(b);
+        if(x == y) return false;
+        root[x] = y;
+        return true;
+    }
+
+    public static void main(String[] args) throws Exception {
+        // 0. Input + Construct Tree
+
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        Q = Integer.parseInt(st.nextToken());
+
+        queries = new Query[Q];
+        cantUnion = new BitSet(Q);
+        tree = new List[N+1];
+        root = new int[N+1];
+        for(int i=1;i<=N;i++) {
+            root[i] = i;
+            tree[i] = new ArrayList<>();
+        }
+        for(int i=0;i<Q;i++) {
+            st = new StringTokenizer(br.readLine());
+            if ("+".equals(st.nextToken())) {
+                int a = Integer.parseInt(st.nextToken());
+                int b = Integer.parseInt(st.nextToken());
+                if(union(a,b)) {
+                    tree[a].add(b);
+                    tree[b].add(a);
+                }
+                else {
+                    cantUnion.set(i);
+                }
+                queries[i] = new Query(a, b);
+            }
+            else {
+                queries[i] = new Query(Integer.parseInt(st.nextToken()));
+            }
+        }
+
+        // 1. DFS
+        parent = new int[N+1];
+        depth = new int[N+1];
+        dfs(1, 0, 0);
+
+        // 2. Count Non-bridge
+
+        root = new int[N+1];
+        for(int i=1;i<=N;i++) {
+            root[i] = i;
+        }
+        int nonBridges = 0;
+        for(int i=0;i<Q;i++) {
+            Query query = queries[i];
+            int type = query.type, a = query.a, b = query.b;
+            if(type == 1) {
+                if(!cantUnion.get(i)) continue;
+                a = find(a);
+                b = find(b);
+                while(a != b) {
+                    nonBridges++;
+                    if(depth[a] > depth[b]) {
+                        union(a, parent[a]);
+                        a = find(parent[a]);
+                    }
+                    else {
+                        union(b, parent[b]);
+                        b = find(parent[b]);
+                    }
+                }
+            }
+            else {
+                if(nonBridges <= a && a <= N-1) {
+                    bw.write("JAH\n");
+                }
+                else {
+                    bw.write("EI\n");
+                }
+            }
+        }
+        bw.close();
+    }
+
+    public static void dfs(int cur, int par, int dep) {
+        parent[cur] = par;
+        depth[cur] = dep;
+        for(int nxt : tree[cur]) if(nxt != par) {
+            dfs(nxt, cur, dep+1);
+        }
+    }
+
+}
+```