Knuth–Morris–Pratt algorithm

Author: aladin002dz

Bit-Manipulation/BinaryCountSetBits.js

@@ -16,7 +16,7 @@ function BinaryCountSetBits(a) {
 
   let count = 0
   while (a) {
-    a &= (a - 1)
+    a &= a - 1
     count++
   }
 

Maths/AutomorphicNumber.js

@@ -35,6 +35,6 @@ export const isAutomorphic = (n) => {
     n = Math.floor(n / 10)
     n_sq = Math.floor(n_sq / 10)
   }
-  
+
   return true
 }

Maths/test/AutomorphicNumber.test.js

@@ -9,19 +9,19 @@ describe('AutomorphicNumber', () => {
   })
 
   test.each([
-    { n: -3 , expected: false },
-    { n: -25 , expected: false },
+    { n: -3, expected: false },
+    { n: -25, expected: false }
   ])('should return false when n is negetive', ({ n, expected }) => {
     expect(isAutomorphic(n)).toBe(false)
   })
 
   test.each([
-    { n: 7 , expected: false },
-    { n: 83 , expected: false },
-    { n: 0 , expected: true },
-    { n: 1 , expected: true },
-    { n: 376 , expected: true },
-    { n: 90625 , expected: true },
+    { n: 7, expected: false },
+    { n: 83, expected: false },
+    { n: 0, expected: true },
+    { n: 1, expected: true },
+    { n: 376, expected: true },
+    { n: 90625, expected: true }
   ])('should return $expected when n is $n', ({ n, expected }) => {
     expect(isAutomorphic(n)).toBe(expected)
   })

Project-Euler/Problem006.js

@@ -1,8 +1,8 @@
 // https://projecteuler.net/problem=6
 
 export const squareDifference = (num = 100) => {
-  let sumOfSquares = (num)*(num+1)*(2*num+1)/6
-  let sums = (num*(num+1))/2
-  
+  let sumOfSquares = (num * (num + 1) * (2 * num + 1)) / 6
+  let sums = (num * (num + 1)) / 2
+
   return sums ** 2 - sumOfSquares // difference of square of the total sum and sum of squares
 }

Search/InterpolationSearch.js

@@ -36,4 +36,4 @@ export function interpolationSearch(arr, key) {
   }
 
   return -1
-}
+}

Search/KMP.js

@@ -0,0 +1,57 @@
+/*
+ * Implements the Knuth-Morris-Pratt (KMP) algorithm for pattern searching.
+ *
+ * The KMP algorithm is a string searching algorithm that utilizes the concept of prefix tables or failure functions
+ * to efficiently match patterns in strings. It avoids unnecessary comparisons by taking advantage of the information
+ * gained from previous comparisons.
+ *
+ * This implementation constructs a prefix table that stores the longest proper prefix that is also a suffix for each
+ * prefix of the pattern. This table is then used to guide the pattern matching process, skipping over characters that
+ * are known to not match.
+ *
+ * The algorithm returns the starting index of the first occurrence of the pattern in the text. If the pattern is not
+ * found, the algorithm returns -1.
+ *
+ * Reference: https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm
+ */
+
+function KMPSearch(text, pattern) {
+  let lps = new Array(pattern.length).fill(0)
+  computeLPS(pattern, lps)
+  let i = 0
+  let j = 0
+  while (i < text.length) {
+    if (pattern[j] == text[i]) {
+      j++
+      i++
+    }
+    if (j == pattern.length) {
+      return i - j
+    } else if (i < text.length && pattern[j] != text[i]) {
+      if (j != 0) j = lps[j - 1]
+      else i = i + 1
+    }
+  }
+  return -1
+}
+
+function computeLPS(pattern, lps) {
+  let len = 0
+  let i = 1
+  while (i < pattern.length) {
+    if (pattern[i] == pattern[len]) {
+      len++
+      lps[i] = len
+      i++
+    } else {
+      if (len != 0) {
+        len = lps[len - 1]
+      } else {
+        lps[i] = 0
+        i++
+      }
+    }
+  }
+}
+
+export { KMPSearch }

Search/test/KMP.test.js

@@ -0,0 +1,27 @@
+import { KMPSearch } from '../KMP'
+
+describe('Rabin-Karp Search', function () {
+  test('KMP algorithm test 1', () => {
+    let text = 'AAAAA'
+    let pattern = 'AAA'
+    expect(KMPSearch(text, pattern)).toBe(0)
+  })
+
+  test('KMP algorithm test 2', () => {
+    let text = 'ABABDABACDABABCABAB'
+    let pattern = 'DABA'
+    expect(KMPSearch(text, pattern)).toBe(4)
+  })
+
+  test('KMP algorithm test 3', () => {
+    let text = 'ABABDABACDABABCABAB'
+    let pattern = 'ABABCABAB'
+    expect(KMPSearch(text, pattern)).toBe(10)
+  })
+
+  test('KMP algorithm test 4', () => {
+    let text = 'ABABDABACDABABCABAB'
+    let pattern = 'XYZ'
+    expect(KMPSearch(text, pattern)).toBe(-1)
+  })
+})