commit 6099f6d242f1e282d9e26196f68c0e371e1ab150
Author: Tilman Kranz <tilman.kranz@b1-systems.de>
Date:   Sat Aug 20 09:51:37 2022 +0200

    Initial commit

diff --git a/README.md b/README.md
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+# Transform Set of Strings to Common Prefix Notation
+
+## Description
+
+Presented with a series of lines on standard input, the program will
+print an expression on standard output that denotes the line strings
+in a syntax described in <https://tk-sls.de/wp/6071>.
+
+The expression is suitable for Bourne Again Shell brace expansion.
+
+## Test
+
+```
+$ python3 trie.py << EOF
+a
+ab
+abc
+EOF
+```
+
+Expected output:
+
+```
+a{,b{,c}}
+```
+
+Test if the output is accurate:
+
+```
+$ bash -c 'echo a{,b{,c}}'
+```
+
+Expected output:
+
+```
+a ab abc
+```
+
diff --git a/trie.py b/trie.py
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+#!/usr/bin/env python
+# author: Tilman Kranz <t.kranz@tk-sls.de>
+# license: MIT License <https://opensource.org/licenses/MIT>
+# summary: Transform a series of lines into a common prefix notation.
+import sys
+
+# thanks: https://www.adamsmith.haus/python/answers/how-to-create-a-trie-in-python
+def construct_trie(word_list):
+    root = dict()
+    for word in word_list:
+        level = root
+        l = len(word)
+        last = l - 1
+
+        for i in range(l):
+            letter = word[i]
+            if letter not in level:
+                level[letter] = dict()
+            if i == last:
+                level[letter][''] = dict()
+            level = level[letter]
+
+    return root
+
+def print_trie(trie):
+    length = len(trie)
+
+    if length == 0:
+        return
+
+    if length > 1:
+        sys.stdout.write("{")
+
+    count = 1
+
+    for k in trie:
+        if k == '{' or k == ',' or k == '}':
+            sys.stdout.write('\\')
+
+        sys.stdout.write(k)
+
+        print_trie(trie[k])
+
+        if count < length:
+            sys.stdout.write(",")
+
+        count += 1
+
+    if length > 1:
+        sys.stdout.write("}")
+
+lines = []
+
+for line in sys.stdin:
+    stripped = line.strip()
+
+    if stripped != "":
+        lines.append(stripped)
+
+trie = construct_trie(lines)
+# -DEBUG- Dump trie datastructure to standard output.
+# print(trie)
+print_trie(trie)
+sys.stdout.write("\n")