Create ColumnarTranspositionCipher.java

ColumnarTranspositionCipher.java

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+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.Scanner;
+
+public class ColumnarTranspositionCipher {
+
+    public static String encrypt(String plaintext, String key) {
+        int numCols = key.length();
+        int numRows = (int) Math.ceil((double) plaintext.length() / numCols);
+        char[][] grid = new char[numRows][numCols];
+        int index = 0;
+        for (int i = 0; i < numRows; i++) {
+            for (int j = 0; j < numCols; j++) {
+                if (index < plaintext.length()) {
+                    grid[i][j] = plaintext.charAt(index++);
+                } else {
+                    grid[i][j] = ' '; 
+                }
+            }
+        }
+        Integer[] keyOrder = new Integer[numCols];
+        for (int i = 0; i < numCols; i++) {
+            keyOrder[i] = i;
+        }
+        Arrays.sort(keyOrder, Comparator.comparingInt(i -> key.charAt(i)));
+        StringBuilder ciphertext = new StringBuilder();
+        for (int i : keyOrder) {
+            for (int j = 0; j < numRows; j++) {
+                ciphertext.append(grid[j][i]);
+            }
+        }
+        return ciphertext.toString().trim(); 
+    }
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Enter the plaintext: ");
+        String plaintext = scanner.nextLine().replaceAll("\\s+", ""); 
+        System.out.print("Enter the key: ");
+        String key = scanner.nextLine();
+        String encryptedText = encrypt(plaintext, key);
+        System.out.println("Encrypted Text: " + encryptedText);
+    }
+}