diff --git a/src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java b/src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java index 3f33fc17b9b0..ad7835bdbb97 100644 --- a/src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java +++ b/src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java @@ -1,41 +1,38 @@ package com.thealgorithms.strings.zigZagPattern; final class ZigZagPattern { + private ZigZagPattern() { } + /** + * Encodes a given string into a zig-zag pattern. + * + * @param s the input string to be encoded + * @param numRows the number of rows in the zigzag pattern + * @return the encoded string in zigzag pattern format + */ public static String encode(String s, int numRows) { if (numRows < 2 || s.length() < numRows) { return s; } - int start = 0; - int index = 0; - int height = 1; - int depth = numRows; - char[] zigZagedArray = new char[s.length()]; - while (depth != 0) { - int pointer = start; - int heightSpace = 2 + ((height - 2) * 2); - int depthSpace = 2 + ((depth - 2) * 2); - boolean bool = true; - while (pointer < s.length()) { - zigZagedArray[index++] = s.charAt(pointer); - if (heightSpace == 0) { - pointer += depthSpace; - } else if (depthSpace == 0) { - pointer += heightSpace; - } else if (bool) { - pointer += depthSpace; - bool = false; - } else { - pointer += heightSpace; - bool = true; + + StringBuilder result = new StringBuilder(s.length()); + int cycleLength = 2 * numRows - 2; + + for (int row = 0; row < numRows; row++) { + for (int j = row; j < s.length(); j += cycleLength) { + result.append(s.charAt(j)); + + if (row > 0 && row < numRows - 1) { + int diagonal = j + cycleLength - 2 * row; + if (diagonal < s.length()) { + result.append(s.charAt(diagonal)); + } } } - height++; - depth--; - start++; } - return new String(zigZagedArray); + + return result.toString(); } } diff --git a/src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java b/src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java index 518bfab80f08..2cbbfe3d2dd8 100644 --- a/src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java +++ b/src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java @@ -6,10 +6,14 @@ public class ZigZagPatternTest { @Test - public void palindrome() { + public void testZigZagPattern() { String input1 = "HelloWorldFromJava"; String input2 = "javaIsAProgrammingLanguage"; Assertions.assertEquals(ZigZagPattern.encode(input1, 4), "HooeWrrmalolFJvlda"); Assertions.assertEquals(ZigZagPattern.encode(input2, 4), "jAaLgasPrmgaaevIrgmnnuaoig"); + // Edge cases + Assertions.assertEquals("ABC", ZigZagPattern.encode("ABC", 1)); // Single row + Assertions.assertEquals("A", ZigZagPattern.encode("A", 2)); // numRows > length of string + Assertions.assertEquals("", ZigZagPattern.encode("", 3)); // Empty string } }