[20250705] BOJ / G3 / 피리 부는 사나이 / 이강현

Author: lkhyun

lkhyun/202507/5 BOJ G3 피리 부는 사나이.md

@@ -0,0 +1,91 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main{
+    static class pos{
+        int i,j;
+        pos(int i,int j){
+            this.i=i;
+            this.j=j;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if(this == obj) return true;
+            if(obj == null || getClass() != obj.getClass()) return false;
+            pos other = (pos)obj;
+            return i==other.i && j==other.j;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(i, j);
+        }
+    }
+    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 pos[][] 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 pos[N][M];
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+                parent[i][j] = new pos(i,j);
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            String line = br.readLine();
+            for (int j = 0; j < M; j++) {
+                char cmd = line.charAt(j);
+                if(cmd == 'U' && i != 0){
+                    merge(i,j,i-1,j);
+                }else if(cmd == 'D' && i != N-1){
+                    merge(i,j,i+1,j);
+                }else if(cmd == 'L' && j != 0){
+                    merge(i,j,i,j-1);
+                }else if(cmd == 'R' && j != M-1){
+                    merge(i,j,i,j+1);
+                }
+            }
+        }
+        Set<pos> s = new HashSet<>();
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+                s.add(find(i,j));
+            }
+        }
+        bw.write(s.size()+"");
+        bw.close();
+    }
+    static pos find(int i,int j){
+        if(parent[i][j] != null){
+            if(parent[i][j].i == i && parent[i][j].j == j){
+                return parent[i][j];
+            }
+            else{
+                return parent[i][j] = find(parent[i][j].i,parent[i][j].j);
+            }
+        }
+        return null;
+    }
+    static void merge(int i,int j,int k,int l){
+        pos a = find(i,j);
+        pos b = find(k,l);
+
+        if(a != null && b != null){
+            if(a.equals(b)){
+                return;
+            }else{
+                parent[a.i][a.j] = b;
+            }
+        }
+    }
+}
+```