Merge pull request neetcode-gh#491 from anjola-adeuyi/main

269 Alien Dictionary python

Author: neetcode-gh

python/269-Alien-Dictionary.py

@@ -0,0 +1,37 @@
+class Solution:
+    def alienOrder(self, words: List[str]) -> str:
+        adj = {char: set() for word in words for char in word}
+
+        for i in range(len(words)-1):
+          w1, w2 = words[i], words[i + 1]
+          minLen = min(len(w1), len(w2))
+          if len(w1) > len(w2) and w1[:minLen] == w2[:minLen]:
+            return ''
+          for j in range(minLen):
+            if w1[j] != w2[j]:
+              print(w1[j], w2[j])
+              adj[w1[j]].add(w2[j])
+              break
+
+        visited = {} # {char: bool} False visited, True current path
+        res = []
+
+        def dfs(char):
+          if char in visited:
+            return visited[char]
+
+          visited[char] = True
+
+          for neighChar in adj[char]:
+            if dfs(neighChar):
+              return True
+
+          visited[char] = False
+          res.append(char)
+
+        for char in adj:
+          if dfs(char):
+            return ''
+
+        res.reverse()
+        return ''.join(res)