Feat(BFS_algo): Implements breadth first-search algo to count the num…

NumberOfIslands.py

@@ -0,0 +1,59 @@
+from collections import deque
+
+class Queue:
+    def __init__(self):
+        self.items = deque()
+
+    def is_empty(self):
+        return not self.items
+
+    def enqueue(self, item):
+        self.items.append(item)
+
+    def dequeue(self):
+        return self.items.popleft()
+
+class Solution:
+
+      def is_valid(self,grid, row, col):
+          rows = len(grid)
+          cols = len(grid[0])
+          return 0 <= row < rows and 0 <= col < cols and grid[row][col] == '1'
+      def bfs(self, grid, row,col):
+
+        directions = [
+            (0,1), # right
+            (0,-1), # left 
+            (-1,0), # up
+            (1,0), # down
+            ]
+
+        q = Queue()
+        q.enqueue((row,col))
+        grid[row][col] = '0'
+        while not q.is_empty():
+            curr_row, curr_col = q.dequeue()
+            for i,j in directions:
+                new_row = i + curr_row
+                new_col = j + curr_col
+                #! if the new offset is '1' (valid) and unvisited  
+                if self.is_valid(grid, new_row, new_col):
+                    q.enqueue((new_row, new_col))
+                    grid[new_row][new_col] = '0' #* end of bfs
+
+      def numIslands(self, grid: List[List[str]]) -> int:
+        if not grid:
+            return 0
+        rows = len(grid)
+        cols = len(grid[0])
+        islands = 0
+        for i in range(rows):
+            for j in range(cols):
+              if grid[i][j] == "1":
+                  islands = islands+1
+                  self.bfs(grid, i, j)
+        return islands
+
+if __name__ == "__main__":
+    s = Solution()
+