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solutions/battle-of-the-brains-2026/Island.java

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+// General imports
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.StringTokenizer;
+
+public class Island {
+  static int N, M;
+  static int[][] grid;
+  static boolean[][] visited;
+  static Map<Integer, Integer> islands = new HashMap<>();
+  public static void main(String[] args) throws IOException {
+    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    StringTokenizer st = new StringTokenizer(br.readLine());
+    N = Integer.parseInt(st.nextToken());
+    M = Integer.parseInt(st.nextToken());
+    grid = new int[N][M];
+    visited = new boolean[N][M];
+    for (int i = 0; i < N; i++) {
+      st = new StringTokenizer(br.readLine());
+      for (int j = 0; j < M; j++) {
+        int cell = Integer.parseInt(st.nextToken());
+        grid[i][j] = cell;
+      }
+    }
+    br.close();
+    for (int i = 0; i < N; i++) {
+      for (int j = 0; j < M; j++) {
+        if (visited[i][j]) continue;
+        if (grid[i][j] > 0) {
+          islands.put(grid[i][j], islands.getOrDefault(grid[i][j], 0) + 1);
+          search(grid[i][j], i, j);
+        } else {
+          visited[i][j] = true;
+        }
+      }
+    }
+    if (islands.size() == 0) {
+      System.out.println(0);
+      return;
+    }
+    for (Map.Entry<Integer, Integer> e : islands.entrySet()) {
+      int terrainNumber = e.getKey();
+      int islandNum = e.getValue();
+      System.out.printf("%d %d%n", terrainNumber, islandNum);
+    }
+  }
+
+  static void search(int val, int i, int j) {
+    if (visited[i][j]) return;
+    visited[i][j] = true;
+    for (int dir = 0; dir < 4; dir++) {
+      switch(dir) {
+        case 0:
+          if (j + 1 < M && grid[i][j + 1] == val) {
+            search(val, i, j + 1);
+          }
+          break;
+        case 1:
+          if (i + 1 < N && grid[i + 1][j] == val) {
+            search(val, i + 1, j);
+          }
+          break;
+        case 2:
+          if (j - 1 >= 0 && grid[i][j - 1] == val) {
+            search(val, i, j - 1);
+          }
+          break;
+        case 3:
+          if (i - 1 >= 0 && grid[i - 1][j] == val) {
+            search(val, i - 1, j);
+          }
+          break;
+      }
+    }
+  }
+}