694. Number of Distinct Islands

Author: Partho Biswas

README.md

@@ -540,6 +540,7 @@ BFS, DFS, Dijkstra, Floyd–Warshall, Bellman-Ford, Kruskal, Prim's, Minimum Spa
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 </p>

leetcode.com/python/694_Number_of_Distinct_Islands.py

@@ -0,0 +1,28 @@
+class Solution(object):
+    def numDistinctIslands(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: int
+        """
+        distinctIlandSet = set()
+        rows, cols = len(grid), len(grid[0])
+        for row in range(rows):
+            for col in range(cols):
+                if grid[row][col] == 1:
+                    currentIlanndPosition = []
+                    self.numDistinctIslandsDFSHelper(grid, currentIlanndPosition, row, col, 0, 0)
+                    distinctIlandSet.add(tuple(currentIlanndPosition))
+        return len(distinctIlandSet)
+
+    def numDistinctIslandsDFSHelper(self, grid, currentIlanndPosition, row, col, referrenceRowPos, referrenceColPos):
+        grid[row][col] = -1  # marking this cell as visited
+        currentIlanndPosition.append((referrenceRowPos, referrenceColPos))
+        neighbours = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+        for neighbour in neighbours:
+            dr, dc = neighbour
+            nextR, nextC = row + dr, col + dc
+            nextReferrenceRowPos, nextReferrenceColPos = referrenceRowPos + dr, referrenceColPos + dc
+            if 0 <= nextR < len(grid) and 0 <= nextC < len(grid[0]) and grid[nextR][nextC] == 1:
+                self.numDistinctIslandsDFSHelper(grid, currentIlanndPosition, nextR, nextC, nextReferrenceRowPos,
+                                                 nextReferrenceColPos)
+