DICTIONARY 180ms

DEF/DICTIONARY/Queue-ri.py

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+import sys
+from collections import defaultdict
+input = sys.stdin.readline
+
+def main():
+    adj = None
+    visited = None
+    order = None
+
+    def check(order):
+        order = order[::-1]
+        for i in range(1, len(order)):
+            j = i-1
+            if adj[order[i]][order[j]]: return False
+        return order
+
+    def dfs(c):
+        visited[c] = 1
+        for e in adj[c]:
+            if not visited[e]:
+                dfs(e)
+        order.append(c)
+
+    for TC in range(int(input())):
+        adj = defaultdict(lambda: defaultdict(int))
+        N = int(input())
+        words = []
+        for i in range(N): words.append(input().rstrip())
+        for i in range(1, N): # adj initialization
+            j = i-1
+            L = min(len(words[j]), len(words[i]))
+            for k in range(L):
+                if words[j][k] != words[i][k]:
+                    adj[words[j][k]][words[i][k]] = 1
+                    break # following characters are meaningless
+
+        visited = defaultdict(int)
+        order = []
+        for c in reversed('abcdefghijklmnopqrstuvwxyz'):
+            if not visited[c]: dfs(c)
+        order = check(order)
+        print(''.join(order) if order else 'INVALID HYPOTHESIS')
+
+if __name__ == '__main__':
+    main()