Leetcode Problem 79 - Word Search

Contributor/word_search_79.py

@@ -0,0 +1,32 @@
+def exist(self, board, word):
+        def backtrack(word, i, j, m, n):
+            if board[i][j] != word[self.l]:
+                return
+            visited.add((i, j))
+            self.l += 1
+            if self.l == len(word):
+                self.is_found = True
+                return 
+            for di, dj in [(0, 1), (1, 0), (0, -1), (-1, 0)]:
+                i1, j1 = i + di, j + dj
+                if 0 <= i1 < m and 0 <= j1 < n and (i1, j1) not in visited:
+                    backtrack(word, i1, j1, m, n)
+                    if self.is_found:
+                        return 
+            visited.remove((i, j))
+            self.l -= 1
+
+        if not board or not board[0]:
+            return False
+        if word == '':
+            return True
+        m, n = len(board), len(board[0])
+        self.is_found = False
+        self.l = 0
+        visited = set()
+        for i in range(m):
+            for j in range(n):
+                backtrack(word, i, j, m, n)
+                if self.is_found:
+                    return True
+        return False