Added Lab2/Lab3 IS

IS/Lab/Lab1/q3_playfair.py

@@ -1,18 +1,14 @@
 def generate_playfair_matrix(key):
     key = ''.join(sorted(set(key.upper()), key=key.upper().index))
-    alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-    matrix = []
-
-    for char in key:
-        if char not in matrix and char != 'J':
-            matrix.append(char)
-
-    for char in alphabet:
-        if char not in matrix and char != 'J':
-            matrix.append(char)
-
-    playfair_matrix = [matrix[i:i+5] for i in range(0, len(matrix), 5)]
-    return playfair_matrix
+    alphabet = "ABCDEFGHIKLMNOPQRSTUVWXYZ"  # J omitted
+    unique = []
+    for ch in key:
+        if ch != 'J' and ch not in unique:
+            unique.append(ch)
+    for ch in alphabet:
+        if ch not in unique:
+            unique.append(ch)
+    return [unique[i:i+5] for i in range(0, 25, 5)]
 
 def find_pos(matrix, char):
     for row_idx, row in enumerate(matrix):
@@ -22,16 +18,14 @@ def find_pos(matrix, char):
     return None
 
 def prepare_text(text):
-    text = ''.join(filter(str.isalpha, text.upper()))
-    text = text.replace('J', 'I')
-    pairs = []
-    i = 0
+    text = ''.join(ch for ch in text.upper() if ch.isalpha()).replace('J', 'I')
+    pairs, i = [], 0
     while i < len(text):
-        if i + 1 < len(text) and text[i] != text[i+1]:
-            pairs.append(text[i:i+2])
+        if i + 1 < len(text) and text[i] != text[i + 1]:
+            pairs.append(text[i:i + 2])
             i += 2
         else:
-            pairs.append(text[i]+'X')
+            pairs.append(text[i] + 'X')
             i += 1
     return pairs