Add dfs maze search (keon#613)

* [Add] Create maze_search.py

Add maze_search.py in dfs section.

* [Edit] Add description and examples

Add description and examples in maze_search problem.

* [Edit] Add methods in maze_search

Add find_path and dfs methods in dfs_maze_search problem.

* [Edit] Add global variable

Add global variable directions in maze_search problem in dfs section.

* [Edit] Add global variable

Add global variable cnt in maze_search problem in dfs section.

* [Edit] Add return condition

Add return condition of dfs method.

* [Edit] Add code in dfs method

Move i and j following defined directions.

* [Edit] Add code in dfs method

Implement recursive call in dfs method.

* [Fix] Implement dfs method

Fix wrong variable names in dfs method.

* [Edit] Add dfs method call and testing code

Complete find_path method and add testing code.

* [Edit] Delete testing code

* [Edit] Delete global variable

Change global variable directions to local variable.

* [Edit] Delete global variable

Change global variable cnt to local variable.

* [Edit] Add description

Add description in maze_search problem in dfs section.

* [Edit] Add unittest

Implement unittest func. of maze_search problem and edit init file.

* [Edit] Edit unittest

Change wrong test answer.

algorithms/dfs/__init__.py

@@ -3,3 +3,4 @@
 from .pacific_atlantic import *
 from .sudoku_solver import *
 from .walls_and_gates import *
+from .maze_search import *

algorithms/dfs/maze_search.py

@@ -0,0 +1,55 @@
+'''
+Find shortest path from top left column to the right lowest column using DFS.
+only step on the columns whose value is 1
+if there is no path, it returns -1
+(The first column(top left column) is not included in the answer.)
+
+Ex 1)
+If maze is
+[[1,0,1,1,1,1],
+ [1,0,1,0,1,0],
+ [1,0,1,0,1,1],
+ [1,1,1,0,1,1]],
+the answer is: 14
+
+Ex 2)
+If maze is
+[[1,0,0],
+ [0,1,1],
+ [0,1,1]],
+the answer is: -1
+'''
+
+
+def find_path(maze):
+    cnt = dfs(maze, 0, 0, 0, -1)
+    return cnt
+
+
+def dfs(maze, i, j, depth, cnt):
+    directions = [(0, -1), (0, 1), (-1, 0), (1, 0)]
+
+    row = len(maze)
+    col = len(maze[0])
+
+    if i == row - 1 and j == col - 1:
+        if cnt == -1:
+            cnt = depth
+        else:
+            if cnt > depth:
+                cnt = depth
+        return cnt
+
+    maze[i][j] = 0
+
+    for k in range(len(directions)):
+        nx_i = i + directions[k][0]
+        nx_j = j + directions[k][1]
+
+        if nx_i >= 0 and nx_i < row and nx_j >= 0 and nx_j < col:
+            if maze[nx_i][nx_j] == 1:
+                cnt = dfs(maze, nx_i, nx_j, depth + 1, cnt)
+
+    maze[i][j] = 1
+
+    return cnt

tests/test_dfs.py

@@ -3,7 +3,8 @@
     num_islands,
     pacific_atlantic,
     Sudoku,
-    walls_and_gates
+    walls_and_gates,
+    find_path
 )
 
 import unittest
@@ -50,6 +51,14 @@ def test_walls_and_gates(self):
         walls_and_gates(rooms)
         self.assertEqual([[3, -1, 0, 1], [2, 2, 1, -1], [1, -1, 2, -1], [0, -1, 3, 4]], rooms)
 
+class TestMazeSearch(unittest.TestCase):
+    def test_maze_search(self):
+        maze_1 = [[1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1], [1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1]]
+        self.assertEqual(37, find_path(maze_1))
+        maze_2 = [[1,0,1,1,1,1], [1,0,1,0,1,0], [1,0,1,0,1,1], [1,1,1,0,1,1]]
+        self.assertEqual(14, find_path(maze_2))
+        maze_3 = [[1,0,0], [0,1,1], [0,1,1]]
+        self.assertEqual(-1, find_path(maze_3))
 
 if __name__ == "__main__":
     unittest.main()