From e1a2eed0d91dc015110e0fe8709f886399df9f9b Mon Sep 17 00:00:00 2001
From: Graham Cox <graham@grahamcox.co.uk>
Date: Sat, 9 Mar 2024 10:18:55 +0000
Subject: [PATCH] =?UTF-8?q?BAEL-7496:=20Vigen=C3=A8re=20Cipher=20in=20Java?=
 =?UTF-8?q?=20(#16072)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../algorithms/vigenere/VigenereCipher.java   | 69 +++++++++++++++++++
 .../vigenere/VigenereCipherUnitTest.java      | 63 +++++++++++++++++
 2 files changed, 132 insertions(+)
 create mode 100644 algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipher.java
 create mode 100644 algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipherUnitTest.java

diff --git a/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipher.java b/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipher.java
new file mode 100644
index 0000000000..37a7c13d17
--- /dev/null
+++ b/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipher.java
@@ -0,0 +1,69 @@
+package com.baeldung.algorithms.vigenere;
+
+public class VigenereCipher {
+    private final String characters;
+
+    public VigenereCipher() {
+        this("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
+    }
+
+    public VigenereCipher(String characters) {
+        this.characters = characters;
+    }
+
+    public String encode(String input, String key) {
+        String result = "";
+
+        int keyPosition = 0;
+        for (char c : input.toCharArray()) {
+            char k = key.charAt(keyPosition % key.length());
+
+            int charIndex = characters.indexOf(c);
+            int keyIndex = characters.indexOf(k);
+
+            if (charIndex >= 0) {
+                if (keyIndex >= 0) {
+                    int newCharIndex = (charIndex + keyIndex + 1) % characters.length();
+                    c = characters.charAt(newCharIndex);
+
+                }
+
+                keyPosition++;
+            }
+
+            result += c;
+        }
+
+        return result;
+    }
+
+    public String decode(String input, String key) {
+        String result = "";
+
+        int keyPosition = 0;
+        for (char c : input.toCharArray()) {
+            char k = key.charAt(keyPosition % key.length());
+
+            int charIndex = characters.indexOf(c);
+            int keyIndex = characters.indexOf(k);
+
+            if (charIndex >= 0) {
+                if (keyIndex >= 0) {
+                    int newCharIndex = charIndex - keyIndex - 1;
+                    if (newCharIndex < 0) {
+                        newCharIndex = characters.length() + newCharIndex;
+                    }
+                    c = characters.charAt(newCharIndex);
+
+                }
+
+                keyPosition++;
+            }
+
+            result += c;
+        }
+
+        return result;
+    }
+
+}
diff --git a/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipherUnitTest.java b/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipherUnitTest.java
new file mode 100644
index 0000000000..0e61e9c42e
--- /dev/null
+++ b/algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/vigenere/VigenereCipherUnitTest.java
@@ -0,0 +1,63 @@
+package com.baeldung.algorithms.vigenere;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class VigenereCipherUnitTest {
+
+    @Test
+    void encodeBaeldung() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.encode("BAELDUNG", "HELLO");
+
+        Assertions.assertEquals("JFQXSCSS", output);
+    }
+
+    @Test
+    void encodeBaeldungMixedCharacters() {
+        VigenereCipher cipher = new VigenereCipher("JQFVHPWORZSLNMKYCGBUXIEDTA");
+        String output = cipher.encode("BAELDUNG", "HELLO");
+
+        Assertions.assertEquals("DERDPTZV", output);
+    }
+
+    @Test
+    void encodeArticleTitle() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.encode("VEGENERE CIPHER IN JAVA", "BAELDUNG");
+
+        Assertions.assertEquals("XFLQRZFL EJUTIM WU LBAM", output);
+    }
+
+    @Test
+    void encodeArticleTitleMoreCharacters() {
+        VigenereCipher cipher = new VigenereCipher("ABCDEFGHIJKLMNOPQRSTUVWXYZ ");
+        String output = cipher.encode("VEGENERE CIPHER IN JAVA", "BAELDUNG");
+
+        Assertions.assertEquals("XFLQRZELBDNALZEGKOEVEPO", output);
+    }
+
+    @Test
+    void decodeBaeldung() {
+        VigenereCipher cipher = new VigenereCipher();
+        String output = cipher.decode("JFQXSCSS", "HELLO");
+
+        Assertions.assertEquals("BAELDUNG", output);
+    }
+
+    @Test
+    void decodeBaeldungMixedCharacters() {
+        VigenereCipher cipher = new VigenereCipher("JQFVHPWORZSLNMKYCGBUXIEDTA");
+        String output = cipher.decode("DERDPTZV", "HELLO");
+
+        Assertions.assertEquals("BAELDUNG", output);
+    }
+
+    @Test
+    void decodeArticleTitleMoreCharacters() {
+        VigenereCipher cipher = new VigenereCipher("ABCDEFGHIJKLMNOPQRSTUVWXYZ ");
+        String output = cipher.decode("XFLQRZELBDNALZEGKOEVEPO", "BAELDUNG");
+
+        Assertions.assertEquals("VEGENERE CIPHER IN JAVA", output);
+    }
+}