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goingreengoingreen
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Add Union-Find data structure implementation
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‎UnionFindDS/README.markdown

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# Union Find Data Structure
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TODO

‎UnionFindDS/UnioinFindDS.playground/Contents.swift

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//: Playground - noun: a place where people can play
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public class UnionFindDS<T: Hashable> {
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private var index = [T:Int]()
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private var parent = [Int]()
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private var size = [Int]()
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public func addSetWithElement(element: T) {
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index[element] = parent.count
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parent.append(parent.count)
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size.append(1)
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}
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private func findSetByIndexOfElement(index: Int) -> Int {
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if parent[index] == index {
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return index
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} else {
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parent[index] = findSetByIndexOfElement(parent[index])
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return parent[index]
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}
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}
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public func findSetOfElement(element: T) -> Int {
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let indexOfElement = index[element]!
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return findSetByIndexOfElement(indexOfElement)
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}
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public func unionSetsWithElement(firstElement: T, andSecondElement secondElement: T) {
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let firstSet = findSetOfElement(firstElement)
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let secondSet = findSetOfElement(secondElement)
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if (firstSet != secondSet) {
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if (size[firstSet] < size[secondSet]) {
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parent[firstSet] = secondSet;
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size[secondSet] += size[firstSet]
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} else {
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parent[secondSet] = firstSet;
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size[firstSet] += size[secondSet]
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}
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}
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}
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}
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let dsu = UnionFindDS<Int>()
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for i in 1...10 {
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dsu.addSetWithElement(i)
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}
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// now our dsu contains 10 independent sets
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// let's divide our numbers into two sets by divisibility by 2
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for i in 3...10 {
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if i % 2 == 0 {
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dsu.unionSetsWithElement(2, andSecondElement: i)
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} else {
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dsu.unionSetsWithElement(1, andSecondElement: i)
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}
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}
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// check our division
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print(dsu.findSetOfElement(2) == dsu.findSetOfElement(4))
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print(dsu.findSetOfElement(4) == dsu.findSetOfElement(6))
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print(dsu.findSetOfElement(6) == dsu.findSetOfElement(8))
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print(dsu.findSetOfElement(8) == dsu.findSetOfElement(10))
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print(dsu.findSetOfElement(1) == dsu.findSetOfElement(3))
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print(dsu.findSetOfElement(3) == dsu.findSetOfElement(5))
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print(dsu.findSetOfElement(5) == dsu.findSetOfElement(7))
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print(dsu.findSetOfElement(7) == dsu.findSetOfElement(9))
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print(dsu.findSetOfElement(8) == dsu.findSetOfElement(9))
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print(dsu.findSetOfElement(4) == dsu.findSetOfElement(3))
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let dsuForStrings = UnionFindDS<String>()
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let words = ["all", "border", "boy", "afternoon", "amazing", "awesome", "best"]
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dsuForStrings.addSetWithElement("a")
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dsuForStrings.addSetWithElement("b")
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// In that example we divide strings by its first letter
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for word in words {
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dsuForStrings.addSetWithElement(word)
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if word.hasPrefix("a") {
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dsuForStrings.unionSetsWithElement("a", andSecondElement: word)
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} else if word.hasPrefix("b") {
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dsuForStrings.unionSetsWithElement("b", andSecondElement: word)
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}
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}
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print(dsuForStrings.findSetOfElement("a") == dsuForStrings.findSetOfElement("all"))
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print(dsuForStrings.findSetOfElement("all") == dsuForStrings.findSetOfElement("awesome"))
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print(dsuForStrings.findSetOfElement("amazing") == dsuForStrings.findSetOfElement("afternoon"))
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print(dsuForStrings.findSetOfElement("b") == dsuForStrings.findSetOfElement("boy"))
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print(dsuForStrings.findSetOfElement("best") == dsuForStrings.findSetOfElement("boy"))
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print(dsuForStrings.findSetOfElement("border") == dsuForStrings.findSetOfElement("best"))
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print(dsuForStrings.findSetOfElement("amazing") == dsuForStrings.findSetOfElement("boy"))
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print(dsuForStrings.findSetOfElement("all") == dsuForStrings.findSetOfElement("border"))
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‎UnionFindDS/UnioinFindDS.playground/contents.xcplayground

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='osx'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎UnionFindDS/UnioinFindDS.playground/timeline.xctimeline

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<?xml version="1.0" encoding="UTF-8"?>
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<Timeline
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version = "3.0">
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<TimelineItems>
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</TimelineItems>
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</Timeline>

‎UnionFindDS/UnionFindDS.swift

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/*
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Union-Find Data Structure
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Performance:
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adding new set is almost O(1)
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finding set of element is almost O(1)
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union sets is almost O(1)
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*/
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public class UnionFindDS<T: Hashable> {
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private var index = [T:Int]()
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private var parent = [Int]()
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private var size = [Int]()
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public func addSetWithElement(element: T) {
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index[element] = parent.count
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parent.append(parent.count)
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size.append(1)
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}
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private func findSetByIndexOfElement(index: Int) -> Int {
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if parent[index] == index {
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return index
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} else {
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parent[index] = findSetByIndexOfElement(parent[index])
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return parent[index]
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}
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}
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public func findSetOfElement(element: T) -> Int {
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let indexOfElement = index[element]!
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return findSetByIndexOfElement(indexOfElement)
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}
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public func unionSetsWithElement(firstElement: T, andSecondElement secondElement: T) {
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let firstSet = findSetOfElement(firstElement)
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let secondSet = findSetOfElement(secondElement)
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if (firstSet != secondSet) {
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if (size[firstSet] < size[secondSet]) {
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parent[firstSet] = secondSet;
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size[secondSet] += size[firstSet]
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} else {
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parent[secondSet] = firstSet;
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size[firstSet] += size[secondSet]
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}
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}
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}
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}

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