Add Python solution to challenge 162

3 files changed, 136 insertions, 2 deletions

diff --git a/challenge-001/paulo-custodio/go.pl b/challenge-001/paulo-custodio/go.pl
index 3904778b45..b41860b43a 100644
--- a/challenge-001/paulo-custodio/go.pl
+++ b/challenge-001/paulo-custodio/go.pl
@@ -9,8 +9,9 @@ my $nr = sprintf("%03d", $ARGV[0]);
 
 path("challenge-$nr/paulo-custodio")->mkpath;
 #for my $dir (qw(ada awk basic bc brainfuck c cpp d forth fortran lua pascal perl python t)) {
-#    path("challenge-$nr/paulo-custodio/$dir")->mkpath;
-#}
+for my $dir (qw( perl python t )) {
+    path("challenge-$nr/paulo-custodio/$dir")->mkpath;
+}
 
 path("challenge-$nr/paulo-custodio/README")->spew("Solution by Paulo Custodio\n");
 if (! -f "challenge-$nr/paulo-custodio/Makefile") {
diff --git a/challenge-162/paulo-custodio/python/ch-1.py b/challenge-162/paulo-custodio/python/ch-1.py
new file mode 100644
index 0000000000..1b31447b25
--- /dev/null
+++ b/challenge-162/paulo-custodio/python/ch-1.py
@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+# Challenge 162
+#
+# Task 1: ISBN-13
+# Submitted by: Mohammad S Anwar
+# Write a script to generate the check digit of given ISBN-13 code. Please
+# refer wikipedia for more information.
+#
+# Example
+# ISBN-13 check digit for '978-0-306-40615-7' is 7.
+
+import sys
+
+def isbn13_check_digit(isbn):
+    m = 1
+    sum_ = 0
+    isbn = isbn.replace('-', '')
+    for i in range(12):
+        digit = int(isbn[i])
+        sum_ += m * digit
+        m = 3 if m==1 else 1
+    digit = sum_ % 10
+    if digit != 0:
+        digit = 10-digit
+    return digit
+
+print(isbn13_check_digit(sys.argv[1]))
diff --git a/challenge-162/paulo-custodio/python/ch-2.py b/challenge-162/paulo-custodio/python/ch-2.py
new file mode 100644
index 0000000000..aad3aadf83
--- /dev/null
+++ b/challenge-162/paulo-custodio/python/ch-2.py
@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+
+# Challenge 162
+#
+# Task 2: Wheatstone-Playfair
+# Submitted by: Roger Bell_West
+# Implement encryption and decryption using the Wheatstone-Playfair cipher.
+#
+# Examples:
+# (These combine I and J, and use X as padding.)
+#
+# encrypt("playfair example", "hide the gold in the tree stump")
+# = "bmodzbxdnabekudmuixmmouvif"
+#
+# decrypt("perl and raku", "siderwrdulfipaarkcrw") = "thewexeklychallengex"
+
+class WPcipher:
+    def __init__(self, key_phrase):
+        self.key = [[] for _ in range(5)]
+        self.letters = {}
+        self.make_key(key_phrase)
+
+    def make_key(self, key_phrase):
+        row, col = 0, 0
+        for c in (key_phrase.lower() + ''.join(chr(i) for i in range(ord('a'), ord('z') + 1))):
+            if not c.isalpha() or c not in 'abcdefghijklmnopqrstuvwxyz':
+                continue
+            c = 'i' if c == 'j' else c
+            if c in self.letters:
+                continue
+
+            self.key[row].append(c)
+            self.letters[c] = (row, col)
+
+            col += 1
+            if col >= 5:
+                row += 1
+                col = 0
+                if row >= 5:
+                    break
+
+    def peek(self, row, col):
+        return self.key[(row + 5) % 5][(col + 5) % 5]
+
+    def encrypt_pair(self, a, b, direction):
+        for char in (a, b):
+            if char not in 'abcdefghiklmnopqrstuvwxyz':
+                raise ValueError(f"Invalid character: {char}")
+        if a == b:
+            raise ValueError("Characters must not be the same")
+
+        row1, col1 = self.letters[a]
+        row2, col2 = self.letters[b]
+
+        if row1 == row2:
+            return (self.peek(row1, col1 + direction),
+                    self.peek(row2, col2 + direction))
+        elif col1 == col2:
+            return (self.peek(row1 + direction, col1),
+                    self.peek(row2 + direction, col2))
+        else:
+            return (self.peek(row1, col2),
+                    self.peek(row2, col1))
+
+    def encrypt_string(self, text, direction):
+        text = text.lower()
+        out = ""
+        while text:
+            if len(text) == 1:
+                text += "x"
+            if text[0] == text[1:2]:  # repeated first character
+                a = text[0]
+                b = "x"
+                text = text[1:]
+            else:
+                a = text[0]
+                b = text[1]
+                text = text[2:]
+
+            x, y = self.encrypt_pair(a, b, direction)
+            out += x + y
+        return out
+
+    def encrypt(self, text):
+        text = ''.join(filter(str.isalpha, text)).lower().replace('j', 'i')
+        return self.encrypt_string(text, 1)
+
+    def decrypt(self, code):
+        return self.encrypt_string(code, -1)
+
+
+import sys
+
+if len(sys.argv) != 4:
+    raise ValueError("Usage: ch-2.py -e|-d key text")
+
+op, key_phrase, text = sys.argv[1], sys.argv[2], sys.argv[3]
+
+wp = WPcipher(key_phrase)
+if op == "-e":
+    print(wp.encrypt(text))
+elif op == "-d":
+    print(wp.decrypt(text))
+else:
+    raise ValueError("Usage: ch-2.py -e|-d key text")