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Commit bccaf97

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Add Z-Algorithm for Linear-Time String Pattern Matching (#7124)
* Add Z-Algorithm (string pattern matching) with tests * Add Z-Algorithm (string pattern matching) with tests * Add Z-Algorithm (string pattern matching) with tests * Fix checkstyle errors for ZAlgorithm * Fix: clang-format and checkstyle compliance for ZAlgorithm
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‎DIRECTORY.md‎

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- 📄 [Upper](src/main/java/com/thealgorithms/strings/Upper.java)
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- 📄 [ValidParentheses](src/main/java/com/thealgorithms/strings/ValidParentheses.java)
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- 📄 [WordLadder](src/main/java/com/thealgorithms/strings/WordLadder.java)
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- 📄 [ZAlgorithm](src/main/java/com/thealgorithms/strings/ZAlgorithm.java)
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- 📁 **zigZagPattern**
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- 📄 [ZigZagPattern](src/main/java/com/thealgorithms/strings/zigZagPattern/ZigZagPattern.java)
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- 📁 **tree**
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- 📄 [UpperTest](src/test/java/com/thealgorithms/strings/UpperTest.java)
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- 📄 [ValidParenthesesTest](src/test/java/com/thealgorithms/strings/ValidParenthesesTest.java)
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- 📄 [WordLadderTest](src/test/java/com/thealgorithms/strings/WordLadderTest.java)
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- 📄 [ZAlgorithmTest](src/test/java/com/thealgorithms/strings/ZAlgorithmTest.java)
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- 📁 **zigZagPattern**
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- 📄 [ZigZagPatternTest](src/test/java/com/thealgorithms/strings/zigZagPattern/ZigZagPatternTest.java)
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- 📁 **tree**
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/*
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* https://en.wikipedia.org/wiki/Z-algorithm
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*/
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package com.thealgorithms.strings;
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public final class ZAlgorithm {
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private ZAlgorithm() {
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throw new UnsupportedOperationException("Utility class");
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}
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public static int[] zFunction(String s) {
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int n = s.length();
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int[] z = new int[n];
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int l = 0;
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int r = 0;
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for (int i = 1; i < n; i++) {
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if (i <= r) {
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z[i] = Math.min(r - i + 1, z[i - l]);
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}
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while (i + z[i] < n && s.charAt(z[i]) == s.charAt(i + z[i])) {
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z[i]++;
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}
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if (i + z[i] - 1 > r) {
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l = i;
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r = i + z[i] - 1;
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}
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}
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return z;
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}
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public static int search(String text, String pattern) {
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String s = pattern + "$" + text;
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int[] z = zFunction(s);
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int p = pattern.length();
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for (int i = 0; i < z.length; i++) {
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if (z[i] == p) {
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return i - p - 1;
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}
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}
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return -1;
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}
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}
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package com.thealgorithms.strings;
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import static org.junit.jupiter.api.Assertions.assertArrayEquals;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import org.junit.jupiter.api.Test;
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public class ZAlgorithmTest {
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@Test
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void testZFunction() {
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int[] z = ZAlgorithm.zFunction("aaaaa");
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assertArrayEquals(new int[] {0, 4, 3, 2, 1}, z);
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}
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@Test
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void testSearchFound() {
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assertEquals(2, ZAlgorithm.search("abcabca", "cab"));
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}
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@Test
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void testSearchNotFound() {
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assertEquals(-1, ZAlgorithm.search("abcdef", "gh"));
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}
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}

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