Create shortest-path-in-binary-matrix.py

Author: kamyu104

Python/shortest-path-in-binary-matrix.py

@@ -0,0 +1,32 @@
+# Time:  O(n^2)
+# Space: O(n)
+
+import collections
+
+
+class Solution(object):
+    def shortestPathBinaryMatrix(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: int
+        """
+        directions = [(-1, -1), (-1, 0), (-1, 1), \
+                      ( 0, -1), ( 0, 1), \
+                      ( 1, -1), ( 1, 0), ( 1, 1)]
+        result = 0
+        q = collections.deque([(0, 0)])
+        while q:
+            result += 1
+            next_depth = collections.deque()
+            while q:
+                i, j = q.popleft()
+                if 0 <= i < len(grid) and \
+                   0 <= j < len(grid[0]) and \
+                    not grid[i][j]:
+                    grid[i][j] = 1
+                    if i == len(grid)-1 and j == len(grid)-1:
+                        return result
+                    for d in directions:
+                        next_depth.append((i+d[0], j+d[1]))
+            q = next_depth
+        return -1