Added solution to Caesar-cipher

challenges/easy/caesar-cipher/solutions/stefanocroci/solution.py

@@ -0,0 +1,38 @@
+alpha = 'abcdefghijklmnopqrstuvwxyz'
+def encode(phrase, shift):
+    new_phrase = ''
+    for i in range(len(phrase)):
+        if phrase[i].lower() not in alpha:
+            new_phrase += phrase[i]
+            continue
+        # Find the phrase corresponding index in alpha
+        index_alpha = alpha.find(phrase[i].lower())
+        # Use mod to consider the cases in which (index + shift) is more than lenght of alpha
+        new_index = (index_alpha + shift) % len(alpha) 
+        # Convert the output in uppercase if input is uppercase
+        if phrase[i].isupper():
+            new_phrase += alpha[new_index].upper()
+        else:
+            new_phrase += alpha[new_index]
+
+    return new_phrase
+
+def decode(phrase, shift):
+    return encode(phrase, -shift)
+
+while True:
+    print('--------------------------------------------------')
+    start = int(input('Hello, digit 1 to encode a phrase or digit 2 to decode a phrase: '))
+    if start == 1:
+        phrase = input('Please insert the phrase to encode it: ')
+        shift = int(input('Insert the shift amount: '))
+        encoded_phrase = encode(phrase, shift)
+        print(encoded_phrase)
+    elif start == 2:
+        phrase = input('Please insert the phrase to decode it: ')
+        shift = int(input('Insert the shift amount used to encode the phrase: '))
+        decoded_phrase = decode(phrase, shift)
+        print(decoded_phrase)
+    else:
+        print('ERROR! digit one or two')
+