200 graph: methods DFS and BFS

Author: HaFred

python/200_Number_of_Islands.py

@@ -1,3 +1,6 @@
+import unittest
+
+
 class Solution(object):
     def numIslands(self, grid):
         """
@@ -9,19 +12,68 @@ def numIslands(self, grid):
             return 0
         islands = 0
         for i in range(len(grid)):
-            for j in range(len(grid[i])):
+            for j in range(len(grid[i])):  # explore each row, each col
                 if grid[i][j] == '1':
                     self.explore(grid, i, j)
                     islands += 1
         return islands
 
     def explore(self, grid, i, j):
-        grid[i][j] = 'X'
+        grid[i][j] = 'X'  # make explored as 'X', then won't be explore by '1' again
+        # recursively explore all the neighbors
         if i - 1 >= 0 and grid[i - 1][j] == '1':
             self.explore(grid, i - 1, j)
         if j - 1 >= 0 and grid[i][j - 1] == '1':
             self.explore(grid, i, j - 1)
         if i + 1 < len(grid) and grid[i + 1][j] == '1':
             self.explore(grid, i + 1, j)
         if j + 1 < len(grid[i]) and grid[i][j + 1] == '1':
-            self.explore(grid, i, j + 1)
+            self.explore(grid, i, j + 1)
+
+
+class SolutionDFS(object):
+    def numIslands(self, grid):
+        """
+        :type grid: List[List[str]]
+        :rtype: int
+        """
+        # DFS with marks
+        if grid is None or len(grid) == 0:
+            return 0
+        islands = 0
+        self.visited = set()
+        self.rows, self.cols = len(grid), len(grid[0])
+        for r in range(self.rows):
+            for c in range(self.cols):
+                if grid[r][c] == "1" and (r, c) not in self.visited:
+                    self.explore(r, c, grid)
+                    islands += 1
+        return islands
+
+    def explore(self, r, c, grid):
+        if r not in range(self.rows) or c not in range(self.cols) or grid[r][c] == "0" or (r, c) in self.visited:
+            return
+        self.visited.add((r, c))
+        directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
+        for dr, dc in directions:  # explore all the neighbors
+            self.explore(r + dr, c + dc, grid)
+
+
+class Test(unittest.TestCase):
+    grid = [["1", "1", "0", "0", "0"],
+            ["1", "1", "0", "0", "0"],
+            ["0", "0", "1", "0", "0"],
+            ["0", "0", "0", "1", "1"]]
+    expected = 3
+    test_funcs1 = [Solution().numIslands]
+    test_funcs2 = [SolutionDFS().numIslands]
+    test_funcs = test_funcs1 + test_funcs2
+
+    def testNum(self):
+        for test_func in self.test_funcs:
+            self.assertEqual(test_func(self.grid), self.expected)
+            # restore input
+            self.grid = [["1", "1", "0", "0", "0"],
+                         ["1", "1", "0", "0", "0"],
+                         ["0", "0", "1", "0", "0"],
+                         ["0", "0", "0", "1", "1"]]