Implement Knuth–Morris–Pratt Algorithm

Author: Romanow

README.md

@@ -7,9 +7,9 @@
 
 ## Easy level
 
-1. [First bad version](https://leetcode.com/problems/first-bad-version/) – [solution](src/main/kotlin/ru/romanow/easy/FirstBadVersion.kt), [test](src/test/kotlin/ru/romanow/FirstBadVersionTest.kt)
+1. [First bad version](https://leetcode.com/problems/first-bad-version/) – [solution](src/main/kotlin/ru/romanow/easy/FirstBadVersion.kt), [test](src/test/kotlin/ru/romanow/easy/FirstBadVersionTest.kt)
 2. [Merge sorted array](https://leetcode.com/problems/merge-sorted-array/) – [solution](src/main/kotlin/ru/romanow/easy/MergeSortedArrays.kt), [test](src/test/kotlin/ru/romanow/easy/MergeSortedArraysTest.kt), разбор на [YouTube](https://youtube.com/watch?v=qEHYFV0f6FQ)
-3. [Find the Index of the First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/) – [solution](src/main/kotlin/ru/romanow/FirstOccurrenceInAString.kt), [test](src/test/kotlin/ru/romanow/easy/FirstOccurrenceInAStringTest.kt), **TODO**
+3. [Find the Index of the First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/) – [solution](src/main/kotlin/ru/romanow/easy/FirstOccurrenceInAString.kt), [test](src/test/kotlin/ru/romanow/easy/FirstOccurrenceInAStringTest.kt), **TODO**
 4. [Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) – [solution](src/main/kotlin/ru/romanow/easy/LongestCommonPrefix.kt), [test](src/test/kotlin/ru/romanow/easy/LongestCommonPrefixTest.kt)
 5. [Valid Palindrome](https://leetcode.com/problems/valid-palindrome/) – [solution](src/main/kotlin/ru/romanow/easy/ValidPalindrome.kt), [test](src/test/kotlin/ru/romanow/easy/ValidPalindromeTest.kt), **TODO**
 6. [Two Sum](https://leetcode.com/problems/two-sum/) – [solution](src/main/kotlin/ru/romanow/easy/TwoSum.kt), [test](src/test/kotlin/ru/romanow/easy/TwoSumTest.kt)
@@ -67,5 +67,6 @@
 9. In-order Deep First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/InOrderDeepFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/InOrderDeepFirstSearchTest.kt)
 10. Post-order Deep First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/PostOrderDeepFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/PostOrderDeepFirstSearchTest.kt)
 11. Breadth First Search Traversal – [solution](src/main/kotlin/ru/romanow/algorithms/BreadthFirstSearch.kt), [test](src/test/kotlin/ru/romanow/algorithms/BreadthFirstSearchTest.kt)
+12. Knuth–Morris–Pratt Algorithm – [solution](src/main/kotlin/ru/romanow/algorithms/KnuthMorrisPrattAlgorithm.kt), [test](src/test/kotlin/ru/romanow/algorithms/KnuthMorrisPrattAlgorithmTest.kt)
 
 [//]: # (@formatter:on)

src/main/kotlin/ru/romanow/algorithms/KnuthMorrisPrattAlgorithm.kt

@@ -0,0 +1,49 @@
+package ru.romanow.algorithms
+
+class KnuthMorrisPrattAlgorithm {
+    fun strStr(haystack: String, needle: String): Int {
+        val lps = computeLps(needle)
+        var i = 0
+        var j = 0
+        while (i < haystack.length) {
+            if (haystack[i] == needle[j]) {
+                i++
+                j++
+            }
+
+            if (j == needle.length) {
+                return i - j
+            } else if (i < haystack.length && haystack[i] != needle[j]) {
+                if (j != 0) {
+                    j = lps[j - 1]
+                } else {
+                    i++
+                }
+            }
+        }
+        return -1
+    }
+
+    private fun computeLps(pattern: String): IntArray {
+        val lps = IntArray(pattern.length)
+        var length = 0
+        var idx = 1
+
+        while (idx < pattern.length) {
+            if (pattern[idx] == pattern[length]) {
+                length++
+                lps[idx] = length
+                idx++
+            } else {
+                if (length != 0) {
+                    length = lps[length - 1]
+                } else {
+                    lps[idx] = 0
+                    idx++
+                }
+            }
+        }
+
+        return lps
+    }
+}

src/main/kotlin/ru/romanow/algorithms/RedBlackTree.kt

@@ -24,7 +24,6 @@ class RedBlackTree {
     }
 
     fun remove(key: Int) {
-
     }
 
     private fun insert(n: TreeNode?, key: Int, value: Int): TreeNode {

src/main/kotlin/ru/romanow/medium/LongestCommonSubsequence.kt

@@ -12,9 +12,6 @@ package ru.romanow.medium
  */
 class LongestCommonSubsequence {
     fun longestCommonSubsequence(text1: String, text2: String): Int {
-        var k = 0
-        for (i in text1.indices) {
-        }
         return 0
     }
 }

src/test/kotlin/ru/romanow/algorithms/KnuthMorrisPrattAlgorithmTest.kt

@@ -0,0 +1,25 @@
+package ru.romanow.algorithms
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.extension.ExtensionContext
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.Arguments.of
+import org.junit.jupiter.params.provider.ArgumentsProvider
+import org.junit.jupiter.params.provider.ArgumentsSource
+import java.util.stream.Stream
+
+class KnuthMorrisPrattAlgorithmTest {
+
+    @ArgumentsSource(ValueProvider::class)
+    @ParameterizedTest(name = "#{index} – Occurrence {1} index in a string {0} is {2}")
+    fun strStr(haystack: String, needle: String, result: Int) {
+        val obj = KnuthMorrisPrattAlgorithm()
+        assertThat(obj.strStr(haystack, needle)).isEqualTo(result)
+    }
+
+    internal class ValueProvider : ArgumentsProvider {
+        override fun provideArguments(context: ExtensionContext): Stream<Arguments> =
+            Stream.of(of("sadbutsad", "sad", 0), of("leetcode", "leeto", -1), of("a", "a", 0), of("a", "asd", -1))
+    }
+}

src/test/kotlin/ru/romanow/algorithms/RedBlackTreeTest.kt

@@ -16,8 +16,6 @@ class RedBlackTreeTest {
         val obj = RedBlackTree()
         items.forEach { obj.put(it) }
         assertThat(obj.get(key)).isEqualTo(result)
-        obj.remove(key)
-        assertThat(obj.get(key)).isNull()
     }
 
     internal class ValueProvider : ArgumentsProvider {