From da9520012c16cf7c766ed9f361254a28b0d7b138 Mon Sep 17 00:00:00 2001
From: LuigiDotSRC <luigi.terashima@gmail.com>
Date: Sat, 18 Jan 2025 14:04:40 -0500
Subject: [PATCH 1/3] implement `create_square()`

---
 python/solution.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/python/solution.py b/python/solution.py
index e69de29..615f734 100644
--- a/python/solution.py
+++ b/python/solution.py
@@ -0,0 +1,24 @@
+def create_square(key: str):
+    square = [['']*5 for i in range(5)]
+
+    i, j = 0, 0
+    inserted = set()
+    #                       J = I
+    for c in key + "ABCDEFGHIKLMNOPQRSTUVWXYZ":
+        if c in inserted:
+            continue
+        square[i][j] = c
+        inserted.add(c)
+        j += 1
+        if j % 5 == 0:
+            j = 0
+            i += 1
+
+    return square
+
+if __name__ == "__main__":
+
+    key = "SUPERSPY"
+    ciphertext = "IKEWENENXLNQLPZSLERUMRHEERYBOFNEINCHCV"
+
+    print(create_square(key))
\ No newline at end of file

From a18eb618b06a1bb1fad6391993a5569f496eafc1 Mon Sep 17 00:00:00 2001
From: LuigiDotSRC <luigi.terashima@gmail.com>
Date: Sat, 18 Jan 2025 14:33:27 -0500
Subject: [PATCH 2/3] implement decryption, result:
 `HIPPOPOTOMONSTROSESQUIPPEDALIOPHOBIA`

---
 python/solution.py | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/python/solution.py b/python/solution.py
index 615f734..15867a0 100644
--- a/python/solution.py
+++ b/python/solution.py
@@ -1,4 +1,6 @@
-def create_square(key: str):
+from typing import List
+
+def create_square(key: str) -> List[List[str]]:
     square = [['']*5 for i in range(5)]
 
     i, j = 0, 0
@@ -16,9 +18,38 @@ def create_square(key: str):
 
     return square
 
-if __name__ == "__main__":
+def find_char(char: str, square: List[List[str]]) -> tuple[int, int]:
+    for i in range(5):
+        for j in range(5):
+            if square[i][j] == char:
+                return (i,j)
+            
+def decrypt(ciphertext: str, square: List[List[str]]) -> str:
+    bigraphs = [ciphertext[i:i+2] for i in range(0, len(ciphertext), 2)]
+    result = []
+    
+    for b in bigraphs:
+        r1, c1 = find_char(b[0], square)
+        r2, c2 = find_char(b[1], square)
+
+        if r1 == r2:
+            result.append(square[r1][(c1 - 1) % 5])
+            result.append(square[r2][(c2 - 1) % 5])
+
+        elif c1 == c2:
+            result.append(square[(r1 - 1) % 5][c1])
+            result.append(square[(r2 - 1) % 5][c2])
 
+        else:
+            result.append(square[r1][c2])
+            result.append(square[r2][c1])
+
+    result = [c for c in result if c != 'X']
+    return "".join(result)
+
+if __name__ == "__main__":
     key = "SUPERSPY"
     ciphertext = "IKEWENENXLNQLPZSLERUMRHEERYBOFNEINCHCV"
 
-    print(create_square(key))
\ No newline at end of file
+    square = create_square(key)
+    print(decrypt(ciphertext, square))

From 8c8078931048a8561045ea1ed0b43e6ce9aec04b Mon Sep 17 00:00:00 2001
From: LuigiDotSRC <luigi.terashima@gmail.com>
Date: Sat, 18 Jan 2025 14:47:57 -0500
Subject: [PATCH 3/3] formatting and docstrings

---
 python/solution.py | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/python/solution.py b/python/solution.py
index 15867a0..902fb3f 100644
--- a/python/solution.py
+++ b/python/solution.py
@@ -1,6 +1,12 @@
 from typing import List
 
 def create_square(key: str) -> List[List[str]]:
+    """
+    Create a 5x5 Polybius Square
+
+    @param key: The key used to encode the Polybius square
+    @return: 5x5 Matrix representation of the generated square
+    """
     square = [['']*5 for i in range(5)]
 
     i, j = 0, 0
@@ -19,12 +25,26 @@ def create_square(key: str) -> List[List[str]]:
     return square
 
 def find_char(char: str, square: List[List[str]]) -> tuple[int, int]:
+    """
+    Finds the location of a character inside the Polybius Square
+
+    @param char: The character to search for inside the square
+    @param square: The Polybius square generated from the `create_square()` function
+    @return: (row, col) location of the character within the square
+    """
     for i in range(5):
         for j in range(5):
             if square[i][j] == char:
                 return (i,j)
             
 def decrypt(ciphertext: str, square: List[List[str]]) -> str:
+    """
+    Decrypts the input ciphertext https://en.wikipedia.org/wiki/Playfair_cipher
+
+    @param ciphertext: The input ciphertext
+    @param square: The Polybius square generated from the `create_square()` function
+    @return: Plaintext
+    """
     bigraphs = [ciphertext[i:i+2] for i in range(0, len(ciphertext), 2)]
     result = []
     
@@ -52,4 +72,5 @@ def decrypt(ciphertext: str, square: List[List[str]]) -> str:
     ciphertext = "IKEWENENXLNQLPZSLERUMRHEERYBOFNEINCHCV"
 
     square = create_square(key)
+
     print(decrypt(ciphertext, square))