feat: Solve alien-dictionary problem

Author: hu6r1s

alien-dictionary/hu6r1s.py

@@ -0,0 +1,44 @@
+from typing import (
+    List,
+)
+
+import heapq
+    heap = [c for c in indegree if indegree[c] == 0]
+    heapq.heapify(heap)
+    res = []
+    
+
+class Solution:
+    """
+    @param words: a list of words
+    @return: a string which is correct order
+    """
+    def alien_order(self, words: List[str]) -> str:
+        # Write your code here
+        adj = {c: set() for word in words for c in word}
+        indegree = {c: 0 for c in adj}
+    
+        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]:
+                    if w2[j] not in adj[w1[j]]:
+                        adj[w1[j]].add(w2[j])
+                        indegree[w2[j]] += 1
+                    break
+        
+        while heap:
+            c = heapq.heappop(heap)
+            res.append(c)
+            for nei in adj[c]:
+                indegree[nei] -= 1
+                if indegree[nei] == 0:
+                    heapq.heappush(heap, nei)
+        
+        if len(res) != len(adj):
+            return ""
+        
+        return "".join(res)