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Author: coder-2433

Islands2.java

@@ -0,0 +1,105 @@
+package PracticeGraphs;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Scanner;
+
+public class Islands2 {
+
+    public static int findParent(int node, int parent[]) {
+        if (node == parent[node]) {
+            return node;
+        }
+        return parent[node] = findParent(parent[node], parent);
+    }
+
+    public static void union(int u, int v, int parent[]) {
+        int ulp = findParent(u, parent); // Find parent of u
+        int vlp = findParent(v, parent); // Find parent of v
+        if (ulp != vlp) {
+            parent[ulp] = vlp; // Union
+        }
+    }
+
+    public static List<Integer> fun(int[][] arr, int[][] arr2) {
+        int n = arr.length;
+        int m = arr[0].length;
+
+        int parent[] = new int[n * m];
+        Arrays.fill(parent, -1);
+
+        int components = 0;
+        List<Integer> islands = new ArrayList<>();
+
+        // Directions for exploring neighbors (up, right, down, left)
+        int dx[] = {-1, 0, 1, 0};
+        int dy[] = {0, 1, 0, -1};
+
+        for (int[] it : arr2) {
+            int x = it[0];
+            int y = it[1];
+            int cell = x * m + y;
+
+            // If already land, return current number of components
+            if (parent[cell] != -1) {
+                islands.add(components);
+                continue;
+            }
+
+            // Add new land
+            parent[cell] = cell;
+            components++;
+
+            // Check neighbors
+            for (int i = 0; i < 4; i++) {
+                int nx = x + dx[i];
+                int ny = y + dy[i];
+
+                if (nx >= 0 && nx < n && ny >= 0 && ny < m) {
+                    int neighbor = nx * m + ny;
+
+                    if (parent[neighbor] != -1) { // Neighbor is part of the grid
+                        int parentCell = findParent(cell, parent);
+                        int parentNeighbor = findParent(neighbor, parent);
+
+                        if (parentCell != parentNeighbor) {
+                            union(cell, neighbor, parent);
+                            components--; // Merge reduces the number of components
+                        }
+                    }
+                }
+            }
+            islands.add(components);
+        }
+
+        return islands;
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int n = sc.nextInt();
+        int m = sc.nextInt();
+
+        int arr[][] = new int[n][m]; // Initial grid
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                arr[i][j] = sc.nextInt();
+            }
+        }
+
+        int n2 = sc.nextInt();
+        int arr2[][] = new int[n2][2];
+
+        for (int i = 0; i < n2; i++) {
+            for (int j = 0; j < 2; j++) {
+                arr2[i][j] = sc.nextInt();
+            }
+        }
+
+        System.out.println(fun(arr, arr2));
+        sc.close();
+    }
+}