Matrix-Graphs -hard- making a large island by merging islands implementation

Author: rajithst

Diff for: matrix/hard/making_a_large_island.py

@@ -0,0 +1,53 @@
+from typing import List
+
+
+class Solution:
+    def largestIsland(self, grid: List[List[int]]) -> int:
+        rows = len(grid)
+        cols = len(grid[0])
+        visited = []
+        for i in range(rows):
+            visited.append([0] * cols)
+
+        island_colors = 0
+        island_sizes = {}
+        island_sizes[island_colors] = 0
+
+        def flood_fill(x, y, color):
+            grid[x][y] = color
+            visited[x][y] = 1
+            island_sizes[color] += 1
+            coordinates = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+            for dx, dy in coordinates:
+                new_x = x + dx
+                new_y = y + dy
+                if 0 <= new_x < rows and 0 <= new_y < cols:
+                    if grid[new_x][new_y] == 1 and visited[new_x][new_y] == 0:
+                        flood_fill(new_x, new_y, color)
+
+        for i in range(rows):
+            for j in range(cols):
+                if grid[i][j] == 1 and visited[i][j] == 0:
+                    island_colors += 1
+                    island_sizes[island_colors] = 0
+                    flood_fill(i, j, island_colors)
+
+        max_island_size = max(island_sizes.values())
+
+        for ii in range(rows):
+            for jj in range(cols):
+                if grid[ii][jj] == 0:
+                    coordinates = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+                    nei_set = set()
+                    for dx, dy in coordinates:
+                        new_i = ii + dx
+                        new_j = jj + dy
+                        if 0 <= new_i < rows and 0 <= new_j < cols:
+                            nei_set.add(grid[new_i][new_j])
+
+                    this_island_size = 1
+                    for color in nei_set:
+                        this_island_size += island_sizes[color]
+
+                    max_island_size = max(max_island_size, this_island_size)
+        return max_island_size