Added solution

Author: avidLearnerInProgress

01matrix.py

@@ -0,0 +1,27 @@
+class Solution:
+     def updateMatrix(self, A: List[List[int]]) -> List[List[int]]:
+        def validNeighbours(i, j, d):
+            for dx, dy in (1, 0), (-1, 0), (0, 1), (0, -1):
+                ni, nj, dn = i + dx, j + dy, d + 1
+                if 0 <= ni < len(A) and 0 <= nj < len(A[0]):
+                    yield ni, nj, dn
+               
+        def bfs(i, j):
+            dist = collections.defaultdict(lambda: float('inf'))
+            queue = collections.deque([(i, j, 0)])
+            while queue:
+                i, j, d = queue.popleft()
+                if A[i][j] == 0:
+                    return d
+                for ni, nj, dn in validNeighbours(i, j, d):
+                    if dn < dist[(ni, nj)]:
+                        dist[(ni, nj)] = dn
+                        queue.append((ni, nj, dn))
+            return A[i][j]
+           
+       
+        for i in range(len(A)):
+            for j in range(len(A[0])):
+                if A[i][j] == 1:
+                    A[i][j] = bfs(i, j)    
+        return A