[20251007] PGM / Lv2 / 석유 시추 / 김수연

[20251007] PGM / Lv2 / 석유 시추 / 김수연

Author: suyeun84

suyeun84/202510/07 PGM LV2 석유 시추.md

@@ -0,0 +1,86 @@
+```java
+import java.util.*;
+class Solution {
+    static int[][] visited;
+    static int[][] dir = new int[][] {{1,0},{-1,0},{0,1},{0,-1}};
+    static int N, M, answer;
+
+    static int id;
+    static int[] size;
+
+    public int solution(int[][] land) {
+        answer = 0;
+        N = land.length;
+        M = land[0].length;
+        visited = new int[N][M];
+        size = new int[N * M + 1];
+        id = 0;
+
+        // 0 : 빈 땅, 1 : 석유가 있는 땅
+        for (int j = 0; j < M; j++) {
+            int total = 0;
+            Set<Integer> used = new HashSet<>();
+            for (int i = 0; i < N; i++) {
+                if (land[i][j] == 0) continue;
+                if (visited[i][j] == 0) {
+                    id++;
+                    bfs(i, j, land);
+                }
+                int comp = visited[i][j];
+                if (!used.contains(comp)) {
+                    used.add(comp);
+                    total += size[comp];
+                }
+                int ny = i;
+                while (i < N && land[i][j] == 1) i++;
+                if (i != N) i--;
+            }
+            answer = Math.max(answer, total);
+        }
+        return answer;
+    }
+
+    private void bfs(int i, int j, int[][] land) {
+        Queue<Point> q = new LinkedList<>();
+        q.add(new Point(i, j));
+        visited[i][j] = -1;
+        int maxVal = 1;
+
+        while (!q.isEmpty()) {
+            Point cur = q.poll();
+            for (int[] d : dir) {
+                int ny = cur.y + d[0];
+                int nx = cur.x + d[1];
+                if (ny < 0 || ny >= N || nx < 0 || nx >= M) continue;
+                if (land[ny][nx] == 0 || visited[ny][nx] != 0) continue;
+                q.add(new Point(ny, nx));
+                visited[ny][nx] = -1;
+                maxVal++;
+            }
+        }
+
+        q.add(new Point(i, j));
+        visited[i][j] = id;
+        while (!q.isEmpty()) {
+            Point cur = q.poll();
+            for (int[] d : dir) {
+                int ny = cur.y + d[0];
+                int nx = cur.x + d[1];
+                if (ny < 0 || ny >= N || nx < 0 || nx >= M) continue;
+                if (visited[ny][nx] != -1) continue;
+                q.add(new Point(ny, nx));
+                visited[ny][nx] = id;
+            }
+        }
+        size[id] = maxVal;
+    }
+
+    static class Point {
+        int y, x;
+        public Point(int y, int x) {
+            this.y = y;
+            this.x = x;
+        }
+    }
+}
+```