From 0cb71dbf9da3a1a5d653fe9dbbd2e0e1419fb700 Mon Sep 17 00:00:00 2001
From: vaibhavpandey11 <61282732+vaibhavpandey11@users.noreply.github.com>
Date: Sun, 10 May 2020 16:04:15 +0530
Subject: [PATCH] Update chain-words.py

This problem was asked in one of my college assignment.
Here is my solution.
---
 challenges/chain-words.py | 62 +++++++++++++--------------------------
 1 file changed, 20 insertions(+), 42 deletions(-)

diff --git a/challenges/chain-words.py b/challenges/chain-words.py
index 3a194ec..12ecb2e 100644
--- a/challenges/chain-words.py
+++ b/challenges/chain-words.py
@@ -1,42 +1,20 @@
-"""
-#246
-Dropbox
-
-Given a list of words, determine whether the words can be chained to form a circle.
-A word X can be placed in front of another word Y in a circle if the last character of X is same as the first character of Y.
-
-For example, the words ['chair', 'height', 'racket', 'touch', 'tunic'] can form the following circle:
-chair --> racket --> touch --> height --> tunic --> chair.
-
-"""
-
-def checkForCycleHelper(usedWords, remainingWords):
-    if len(remainingWords) == 0:
-        # print(usedWords, end=" ")     # Uncomment to see the chain
-        return True
-    
-    lastLetter = usedWords[-1][-1]
-    for i in range(len(remainingWords)):
-        nextWord = remainingWords[i]
-        if nextWord.startswith(lastLetter) and checkForCycleHelper(usedWords+[nextWord], remainingWords[:i]+remainingWords[i+1:]):
-            return True
-    
-    return False
-
-
-def checkForCycle(words):
-    return checkForCycleHelper([words[0]], words[1:])
-
-def main():
-    print(checkForCycle(["geek", "king"]))                      # True ['geek', 'king']
-    print(checkForCycle(["for", "geek", "rig", "kaf"]))         # True ['for', 'rig', 'geek', 'kaf']
-    print(checkForCycle(["aab", "bac", "aaa", "cda"]))          # True ['aab', 'bac', 'cda', 'aaa']
-    print(checkForCycle(["aaa", "bbb", "baa", "aab"]))          # True ['aaa', 'aab', 'bbb', 'baa']
-    print(checkForCycle(["aaa"]))                               # True ['aaa']
-    print(checkForCycle(["aaa", "bbb"]))                        # False
-    print(checkForCycle(["abc", "efg", "cde", "ghi", "ija"]))   # True ['abc', 'cde', 'efg', 'ghi', 'ija']
-    print(checkForCycle(["ijk", "kji", "abc", "cba"]))          # False
-
-
-if __name__ == "__main__":
-    main()
\ No newline at end of file
+words = eval(input())
+length = len(words)  # number of words
+chain = [words[0]]  # appending first word
+words = words[1:]  # slicing out the first word from words
+for i in range(0, length - 1):
+    for word in words:  # each word in the list
+        break_flag = False  # used to check whether to break the loop or not
+        if word[0] == chain[-1][-1]:  # chain forming condition
+            for temp_word in words:  # each word in the list
+                # checks if the list contains word for further chain formation
+                if len(words) != 1 and word[-1] == temp_word[0]:
+                    chain.append(word)  # appending the word
+                    words.remove(word)  # removing the word to avoid repeated check
+                    break_flag = True  # if word added then no use of further iterations
+                    break
+                elif len(words) == 1: chain.append(word)  # in case only one word is left
+        if break_flag: break  # if word already added stop further iterations
+# checks whether the chain formed is correct or not
+if len(chain) == length and chain[0][0] == chain[-1][-1]: print(chain)
+else: print("Sorry. The words cannot be chained to form a circle")