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Commit 4134403

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Fibonacci algorithm
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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internal class FibonacciMemoizedService2 {
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/**
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* O(n) time complexity
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*/
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fun countFibonacci(n: Int, memo: MutableMap<Int, Long>): Long {
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if (n == 0) {
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return 0
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}
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if (memo[n] != null) {
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return memo.getValue(n)
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}
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if (n <= 2) {
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return 1
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}
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val res = countFibonacci(n - 1, memo) + countFibonacci(n - 2, memo)
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memo[n] = res
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return res
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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internal class FibonacciRecursionService1 {
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/**
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* O(2^n) time complexity
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*/
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fun countFibonacci(n: Int): Long {
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if (n == 0) {
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return 0
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}
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if (n <= 2) {
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return 1
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}
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return countFibonacci(n - 1) + countFibonacci(n - 2)
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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internal class FibonacciTabulatedService3 {
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/**
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* O(n) time complexity
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*/
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fun countFibonacci(n: Int): Long {
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if (n == 0) {
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return 0
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}
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val fibNumbers = ArrayList<Long>(n)
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fibNumbers.addAll(listOf(0, 1, 1))
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for (i in 3..n) {
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val value = fibNumbers[i - 1] + fibNumbers[i - 2]
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fibNumbers.add(value)
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}
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return fibNumbers[n]
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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/**
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* Write a function which takes n number and returns
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* sum from 1 to n inclusive.
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*/
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object Runner {
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@JvmStatic
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fun main(args: Array<String>) {
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val n = 20
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val fibonacciRecursionService1 = FibonacciRecursionService1()
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val fibonacciMemoizedService2 = FibonacciMemoizedService2()
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val fibonacciTabulatedService3 = FibonacciTabulatedService3()
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val result1 = fibonacciRecursionService1.countFibonacci(n)
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val result2 = fibonacciMemoizedService2.countFibonacci(n, HashMap(n))
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val result3 = fibonacciTabulatedService3.countFibonacci(n)
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println("Fibonacci number from $n:")
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println("result1 = $result1")
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println("result2 = $result2")
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println("result3 = $result3")
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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import spock.lang.Specification
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import spock.lang.Unroll
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class FibonacciMemoizedService2Spec extends Specification {
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private final FibonacciMemoizedService2 underTest = new FibonacciMemoizedService2()
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@Unroll
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def 'should return (expectedResult=#expectedResult) for (n=#n)'() {
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when:
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def memo = new HashMap<Integer, Integer>(n)
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def result = underTest.countFibonacci(n, memo)
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then:
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result == expectedResult
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where:
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n | expectedResult
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0 | 0
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1 | 1
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2 | 1
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3 | 2
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4 | 3
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5 | 5
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10 | 55
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15 | 610
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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import spock.lang.Specification
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import spock.lang.Unroll
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class FibonacciRecursionService1Spec extends Specification {
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private final FibonacciRecursionService1 underTest = new FibonacciRecursionService1()
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@Unroll
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def 'should return (expectedResult=#expectedResult) for (n=#n)'() {
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when:
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def result = underTest.countFibonacci(n)
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then:
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result == expectedResult
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where:
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n | expectedResult
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0 | 0
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1 | 1
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2 | 1
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3 | 2
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4 | 3
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5 | 5
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10 | 55
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15 | 610
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}
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}
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package pl.dmichalski.algorithms.algorithms._10_fibonacci
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import spock.lang.Specification
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import spock.lang.Unroll
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class FibonacciTabulatedService3Spec extends Specification {
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private final FibonacciTabulatedService3 underTest = new FibonacciTabulatedService3()
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@Unroll
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def 'should return (expectedResult=#expectedResult) for (n=#n)'() {
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when:
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def result = underTest.countFibonacci(n)
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then:
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result == expectedResult
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where:
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n | expectedResult
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0 | 0
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1 | 1
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2 | 1
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3 | 2
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4 | 3
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5 | 5
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10 | 55
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15 | 610
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}
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}

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