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Commit de0f65c

Browse files
refactored some algorithms in the other/search packages + fixed links in the README files
1 parent 932921e commit de0f65c

23 files changed

+332
-394
lines changed

‎README.md

Lines changed: 10 additions & 11 deletions
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@@ -69,24 +69,23 @@ Content:
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4. package <code>search</code> - search algorithms
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* [Binary search](/src/main/kotlin/search/BinarySearch.kt)
72-
* [Binary search (recursive)](/src/main/kotlin/search/BinarySearchRecursive.kt)
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* [Linear search](/src/main/kotlin/search/LinearSearch.kt)
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5. package <code>other</code> - other algorithms
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* [Factorial](/src/main/kotlin/other/Factorial.kt)
77-
* [Knut Morris Pratt's Algorithm for finding a substring](/src/main/kotlin/other/KnuthMorrisPratt.kt)
78-
* [Levenshtein distance](/src/main/kotlin/other/LevensteinLength.kt)
79-
* [Palindrome](/src/main/kotlin/other/Palindrome.kt)
80-
* [Euclid's algorithm](/src/main/kotlin/other/Euclid.kt)
76+
* [Knut Morris Pratt's Algorithm for finding a substring](/src/main/kotlin/other/KnuthMorrisPrattAlgorithm.kt)
77+
* [Levenshtein distance](/src/main/kotlin/other/LevenshteinLengthAlgorithm.kt)
78+
* [Palindrome](/src/main/kotlin/other/PalindromeAlgorithm.kt)
79+
* [Euclid's algorithm](/src/main/kotlin/other/EuclidAlgorithm.kt)
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* [FizzBuzz](/src/main/kotlin/other/FizzBuzz.kt)
82-
* [Reverse Array](/src/main/kotlin/other/ReverseArray.kt)
83-
* [Sieve of Eratosthenes](/src/main/kotlin/other/SieveOfEratosthenes.kt)
84-
* [Finding the minimum](/src/main/kotlin/other/Min.kt)
85-
* [Finding the maximum](/src/main/kotlin/other/Max.kt)
81+
* [Reverse Array](/src/main/kotlin/other/ReverseArrayAlgorithm.kt)
82+
* [Sieve of Eratosthenes](/src/main/kotlin/other/SieveOfEratosthenesAlgorithm.kt)
83+
* [Finding the minimum](/src/main/kotlin/other/MinAlgorithm.kt)
84+
* [Finding the maximum](/src/main/kotlin/other/MaxAlgorithm.kt)
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* [The square root of a number](/src/main/kotlin/other/Sqrt.kt)
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* [Finite state machine](/src/main/kotlin/other/BinaryDigitsCounter.kt)
88-
* [ParenthesisCheck](/src/main/kotlin/other/ParenthesisCheck.kt)
89-
* [StringEqualsHash](/src/main/kotlin/other/StringEqualsHash.kt)
87+
* [ParenthesisCheck](/src/main/kotlin/other/ParenthesisCheckAlgorithm.kt)
88+
* [StringEqualsHash](/src/main/kotlin/other/StringEqualsHashAlgorithm.kt)
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## Your wishes and ideas
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‎README_ru.md

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@@ -69,24 +69,23 @@
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4. пакет <code>ru.search</code> - алгоритмы поиска
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* [Бинарный поиск](/src/main/kotlin/search/BinarySearch.kt)
72-
* [Бинарный поиск (рекурсивный)](/src/main/kotlin/search/BinarySearchRecursive.kt)
7372
* [Линейный поиск](/src/main/kotlin/search/LinearSearch.kt)
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7574
5. пакет <code>ru.other</code> - другие алгоритмы
7675
* [Факториал числа](/src/main/kotlin/other/Factorial.kt)
77-
* [Алгоритм Кнута Морриса Пратта для поиска подстроки](/src/main/kotlin/other/KnuthMorrisPratt.kt)
78-
* [Расстояние Левенштейна](/src/main/kotlin/other/LevensteinLength.kt)
79-
* [Палиндром](/src/main/kotlin/other/Palindrome.kt)
80-
* [Алгоритм Эвклида](/src/main/kotlin/other/Euclid.kt)
76+
* [Алгоритм Кнута Морриса Пратта для поиска подстроки](/src/main/kotlin/other/KnuthMorrisPrattAlgorithm.kt)
77+
* [Расстояние Левенштейна](/src/main/kotlin/other/LevenshteinLengthAlgorithm.kt)
78+
* [Палиндром](/src/main/kotlin/other/PalindromeAlgorithm.kt)
79+
* [Алгоритм Эвклида](/src/main/kotlin/other/EuclidAlgorithm.kt)
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* [FizzBuzz](/src/main/kotlin/other/FizzBuzz.kt)
82-
* [Алгоритм переворота массива](/src/main/kotlin/other/ReverseArray.kt)
83-
* [Решето Эратосфена](/src/main/kotlin/other/SieveOfEratosthenes.kt)
84-
* [Поиск минимума](/src/main/kotlin/other/Min.kt)
85-
* [Поиск максимума](/src/main/kotlin/other/Max.kt)
81+
* [Алгоритм переворота массива](/src/main/kotlin/other/ReverseArrayAlgorithm.kt)
82+
* [Решето Эратосфена](/src/main/kotlin/other/SieveOfEratosthenesAlgorithm.kt)
83+
* [Поиск минимума](/src/main/kotlin/other/MinAlgorithm.kt)
84+
* [Поиск максимума](/src/main/kotlin/other/MaxAlgorithm.kt)
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* [Квадратный корень из числа](/src/main/kotlin/other/Sqrt.kt)
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* [Конечный автомат](/src/main/kotlin/other/BinaryDigitsCounter.kt)
88-
* [Проверка скобок на корректность](/src/main/kotlin/other/ParenthesisCheck.kt)
89-
* [Сравнение строк с помощью хэша](/src/main/kotlin/other/StringEqualsHash.kt)
87+
* [Проверка скобок на корректность](/src/main/kotlin/other/ParenthesisCheckAlgorithm.kt)
88+
* [Сравнение строк с помощью хэша](/src/main/kotlin/other/StringEqualsHashAlgorithm.kt)
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## Ваши пожелания и идеи
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‎src/main/kotlin/other/FactorialBigWithCache.kt

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@@ -10,18 +10,17 @@ import java.math.BigInteger
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*
1111
* also adding large numbers
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*
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* worst time: O(n)
14+
* the best time: O(1)
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* amount of memory: O(n)
16+
* problem: creating a huge number of BigInteger objects
17+
*
1318
*/
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1520
class FactorialBigWithCache {
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1722
private val cache = hashMapOf<Int, BigInteger>()
1823

19-
/**
20-
* worst time: O(n)
21-
* the best time: O(1)
22-
* amount of memory: O(n)
23-
* problem: creating a huge number of BigInteger objects
24-
*/
2524
fun compute(number: Int) : BigInteger {
2625
if (number <= 1) {
2726
return BigInteger.ONE

‎src/main/kotlin/other/FactorialWithCache.kt

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@@ -6,17 +6,16 @@ package other
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*
77
* optimization: caching previous factorial values
88
*
9+
* worst time: O(n)
10+
* the best time: O(1)
11+
* amount of memory: O(n)
12+
*
913
*/
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1115
class FactorialWithCache {
1216

1317
private val cache = hashMapOf<Int, Int>()
1418

15-
/**
16-
* worst time: O(n)
17-
* the best time: O(1)
18-
* amount of memory: O(n)
19-
*/
2019
fun compute(number: Int) : Int {
2120
if (number <= 1) {
2221
return 1

‎src/main/kotlin/other/KnuthMorrisPratt.kt

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This file was deleted.
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,45 @@
1+
package other
2+
3+
/**
4+
*
5+
* Knut Morris Pratt's Algorithm for finding a substring in a string
6+
*
7+
*/
8+
9+
class KnuthMorrisPrattAlgorithm {
10+
11+
// returns true if the substring is in the string
12+
fun contains(sub: String, str: String) : Boolean {
13+
val summary = "$sub$SEPARATOR$str"
14+
val prefixFunctionValue = prefixFunction(summary)
15+
return prefixFunctionValue.any { value -> value == sub.length }
16+
}
17+
18+
// returns the number of occurrences of a substring in a string
19+
fun count(sub: String, str: String) : Int {
20+
val summary = "$sub$SEPARATOR$str"
21+
return prefixFunction(summary).count { value -> value == sub.length }
22+
}
23+
24+
// returns an array of prefix functions for a string
25+
private fun prefixFunction(str: String) : Array<Int> {
26+
val prefixFunctionsValues = Array(str.length) { 0 }
27+
for (index in 1 until str.length) {
28+
var prefixFunctionValue = prefixFunctionsValues[index - 1]
29+
while (prefixFunctionValue > 0 && str[index] != str[prefixFunctionValue]) {
30+
prefixFunctionValue = prefixFunctionsValues[prefixFunctionValue - 1]
31+
}
32+
if (str[index] == str[prefixFunctionValue]) {
33+
prefixFunctionValue++
34+
}
35+
prefixFunctionsValues[index] = prefixFunctionValue
36+
}
37+
return prefixFunctionsValues
38+
}
39+
40+
companion object {
41+
// delimiter must not occur in source strings
42+
private const val SEPARATOR = "#"
43+
}
44+
45+
}

‎src/main/kotlin/other/LevensteinLength.kt renamed to ‎src/main/kotlin/other/LevenshteinLengthAlgorithm.kt

Lines changed: 1 addition & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,11 +8,8 @@ import java.lang.Integer.min
88
*
99
*/
1010

11-
class LevenshteinLength {
11+
class LevenshteinLengthAlgorithm {
1212

13-
/**
14-
* determines the Levenshtein distance for two strings and returns it
15-
*/
1613
fun compute(str1: String, str2: String) : Int {
1714
val matrix = Array(str1.length + 1) {
1815
Array(str2.length + 1) { 0 }

‎src/main/kotlin/other/Max.kt renamed to ‎src/main/kotlin/other/MaxAlgorithm.kt

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@@ -8,14 +8,11 @@ import java.lang.IllegalArgumentException
88
*
99
*/
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11-
class Max<T:Comparable<T>> {
11+
class MaxAlgorithm {
1212

13-
/**
14-
* returns the maximum element from the list
15-
*/
16-
fun compute(items: List<T>) : T {
13+
fun <T : Comparable<T>> compute(items: List<T>) : T {
1714
if (items.isEmpty()) {
18-
throw IllegalArgumentException("items is empty!")
15+
throw IllegalArgumentException("items list is empty!")
1916
}
2017
var max = items[0]
2118
for (i in 1 until items.size) {
@@ -29,7 +26,10 @@ class Max<T : Comparable<T>> {
2926
/**
3027
* returns the maximum element from the list recursively
3128
*/
32-
fun computeRecursive(items: List<T>) : T {
29+
fun <T : Comparable<T>> computeRecursive(items: List<T>) : T {
30+
if (items.isEmpty()) {
31+
throw IllegalArgumentException("items list is empty!")
32+
}
3333
if (items.size == 1) {
3434
return items.first()
3535
}

‎src/main/kotlin/other/Min.kt renamed to ‎src/main/kotlin/other/MinAlgorithm.kt

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Original file line numberDiff line numberDiff line change
@@ -8,14 +8,11 @@ import java.lang.IllegalArgumentException
88
*
99
*/
1010

11-
class Min<T:Comparable<T>> {
11+
class MinAlgorithm {
1212

13-
/**
14-
* returns the minimum element from the list
15-
*/
16-
fun compute(items: List<T>) : T {
13+
fun <T : Comparable<T>> compute(items: List<T>) : T {
1714
if (items.isEmpty()) {
18-
throw IllegalArgumentException("items is empty!")
15+
throw IllegalArgumentException("items list is empty!")
1916
}
2017
var min = items[0]
2118
for (i in 1 until items.size) {
@@ -26,10 +23,10 @@ class Min<T : Comparable<T>> {
2623
return min
2724
}
2825

29-
/**
30-
* returns the minimum element from the list recursively
31-
*/
32-
funcomputeRecursive(items:List<T>) : T {
26+
fun <T:Comparable<T>> computeRecursive(items:List<T>) : T {
27+
if (items.isEmpty()) {
28+
throwIllegalArgumentException("items list is empty!")
29+
}
3330
if (items.size == 1) {
3431
return items.first()
3532
}

‎src/main/kotlin/search/BinarySearch.kt

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Original file line numberDiff line numberDiff line change
@@ -2,22 +2,56 @@ package search
22

33
/**
44
*
5-
* name: binary search algorithm
5+
* Binary search algorithm only works for sorted lists and arrays
66
*
7-
* description: one of the most important features of this algorithm
8-
* is that it only works for sorted lists and arrays
9-
*
10-
* time: log(n)
7+
* best time: 1
8+
* worst time: log(n)
119
* amount of memory: 1
1210
*
1311
*/
1412

15-
class BinarySearch<T : Comparable<T>> {
13+
class BinarySearch {
14+
15+
// searches for an element in the array and returns the index of the searched element or -1
16+
fun <T : Comparable<T>> search(array: Array<T>, element: T) : Int {
17+
if (array.isEmpty()) return -1
18+
19+
var left = 0
20+
var right = array.size
21+
while (left < right) {
22+
val middle = left + (right - left) / 2
23+
if (array[middle] < element) {
24+
left = middle + 1
25+
} else if (array[middle] > element) {
26+
right = middle
27+
} else {
28+
return middle
29+
}
30+
}
31+
return -1
32+
}
33+
34+
// recursive method
35+
// P.S. The tailrec modifier tells the compiler to optimize the recursion and turn it into an iterative version
36+
tailrec fun <T : Comparable<T>> searchRecursive(array: Array<T>, element: T, left: Int = 0, right: Int = array.size - 1): Int {
37+
if (left <= right) {
38+
val middle = left + (right - left) / 2
39+
if (array[middle] == element) {
40+
return middle
41+
}
42+
return if (array[middle] > element) {
43+
searchRecursive(array, element, left, middle - 1)
44+
} else {
45+
searchRecursive(array, element, middle + 1, right)
46+
}
47+
}
48+
return -1
49+
}
50+
51+
// finds the left border index to insert an element into a sorted array
52+
fun <T : Comparable<T>> leftBound(array: Array<T>, element: T) : Int {
53+
if (array.isEmpty()) return 0
1654

17-
/**
18-
* finds the left border index to insert an element [element] into a sorted array [array]
19-
*/
20-
fun leftBound(array: Array<T>, element: T) : Int {
2155
var left = -1
2256
var right = array.size
2357
while ((right - left) > 1) {
@@ -31,10 +65,10 @@ class BinarySearch<T : Comparable<T>> {
3165
return left
3266
}
3367

34-
/**
35-
* finds the right border index to insert an element [element] into a sorted array [array]
36-
*/
37-
funrightBound(array:Array<T>, element:T) : Int {
68+
// finds the right border index to insert an element into a sorted array
69+
fun <T:Comparable<T>> rightBound(array:Array<T>, element:T) : Int {
70+
if (array.isEmpty()) return-1
71+
3872
var left = -1
3973
var right = array.size
4074
while ((right - left) > 1) {
@@ -48,30 +82,4 @@ class BinarySearch<T : Comparable<T>> {
4882
return right
4983
}
5084

51-
/**
52-
* checks if an element [element] is in an array [array] and returns true if the element is present in the array, false otherwise
53-
*/
54-
fun exists(array: Array<T>, element: T): Boolean {
55-
return search(array, element) != -1
56-
}
57-
58-
/**
59-
* searches for an element [element] in an array [array] and returns the index of the searched element or -1
60-
*/
61-
fun search(array: Array<T>, element: T) : Int {
62-
var left = 0
63-
var right = array.size - 1
64-
while (left <= right) {
65-
val middle = (left + right) / 2
66-
if (array[middle] < element) {
67-
left = middle + 1
68-
} else if (array[middle] > element) {
69-
right = middle
70-
} else {
71-
return middle
72-
}
73-
}
74-
return -1
75-
}
76-
7785
}

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