diff --git a/Chinese Whisper/ChineseWhisper.playground/Contents.swift b/Chinese Whisper/ChineseWhisper.playground/Contents.swift
new file mode 100644
index 000000000..2e9ba14f3
--- /dev/null
+++ b/Chinese Whisper/ChineseWhisper.playground/Contents.swift
@@ -0,0 +1,203 @@
+import Foundation
+
+struct SamplePair {
+
+ let index1: Int
+ let index2: Int
+ let distance: Double
+
+ init(idx1: Int, idx2: Int, distance: Double = 1) {
+ self.distance = distance
+ if (idx1 < idx2) {
+ index1 = idx1
+ index2 = idx2
+ } else {
+ index1 = idx2
+ index2 = idx1
+ }
+ }
+}
+
+struct OrderedSamplePair {
+
+ let index1: Int
+ let index2: Int
+ let distance: Double
+
+ init(idx1: Int, idx2: Int, distance: Double = 1) {
+ self.distance = distance
+ index1 = idx1
+ index2 = idx2
+ }
+}
+
+struct Pair {
+ let index1: Int
+ let index2: Int
+
+ init(idx1: Int, idx2: Int) {
+ index1 = idx1
+ index2 = idx2
+ }
+}
+
+class ChineseWhispers {
+
+ func convertUnorderedToOrdered(edges: [SamplePair]) -> [OrderedSamplePair] {
+ var orderdPairs: [OrderedSamplePair] = []
+ orderdPairs.reserveCapacity(edges.count*2)
+
+ for (i, _) in edges.enumerated() {
+ orderdPairs.append(OrderedSamplePair(idx1: edges[i].index1, idx2: edges[i].index2, distance: edges[i].distance))
+ if edges[i].index1 != edges[i].index2 {
+ orderdPairs.append(OrderedSamplePair(idx1: edges[i].index2, idx2: edges[i].index1, distance: edges[i].distance))
+ }
+ }
+ return orderdPairs.sorted { (a, b) -> Bool in
+ a.index1 < b.index1 || (a.index1 == b.index1 && a.index2 < b.index2)
+ }
+ }
+
+ func findNeighborRanges(edges: [OrderedSamplePair]) -> [Pair] {
+ let numNodes: Int = maxIndexPlusOne(pairs: edges)
+ var neighbors: [Pair] = Array(repeating: Pair(idx1: 0, idx2: 0), count: Int(numNodes))
+ var cur_node: Int = 0
+ var start_idx: Int = 0
+
+ for (index, value) in edges.enumerated() {
+ if value.index1 != cur_node {
+ neighbors[Int(cur_node)] = Pair(idx1: start_idx,
+ idx2: index)
+ start_idx = index
+ cur_node = value.index1
+ }
+ }
+ if !neighbors.isEmpty {
+ neighbors[Int(cur_node)] = Pair(idx1: start_idx,
+ idx2: edges.count)
+ }
+ return neighbors
+ }
+
+ func maxIndexPlusOne(pairs: [OrderedSamplePair]) -> Int {
+ if pairs.count == 0 {
+ return 0
+ }else {
+ var max_idx: Int = 0
+ for (_, value) in pairs.enumerated() {
+ if value.index1 > max_idx {
+ max_idx = value.index1
+ }
+ if value.index2 > max_idx {
+ max_idx = value.index2
+ }
+ }
+ return max_idx + 1
+ }
+
+ }
+
+
+ func chinese_whispers<T>(
+ objects: [T],
+ distanceFunction: (T, T) -> Double,
+ eps: Double,
+ numIterations: Int) -> [Int] {
+ var edges: [SamplePair] = []
+ guard !objects.isEmpty else {
+ return []
+ }
+ for i in 0...objects.count-1 {
+ for j in i...objects.count-1 {
+ let length = distanceFunction(objects[i], objects[j])
+ if length < eps {
+ edges.append(SamplePair(idx1: i, idx2: j))
+ }
+ }
+ }
+ return chinese_whispers(edges: edges, numIterations: numIterations)
+ }
+
+ func chinese_whispers(
+ edges: [SamplePair],
+ numIterations: Int) -> [Int] {
+ let orderdEdges = convertUnorderedToOrdered(edges: edges)
+ return chinese_whispers(edges: orderdEdges, numIterations: numIterations)
+ }
+
+ func chinese_whispers(
+ edges: [OrderedSamplePair],
+ numIterations: Int) -> [Int] {
+ let neighbors = findNeighborRanges(edges: edges)
+ var labels: [Int] = Array<Int>(repeating: 0, count: neighbors.count)
+ for i in 0...neighbors.count-1 {
+ labels[i] = i
+ }
+
+ for _ in 0..<(neighbors.count * numIterations) {
+
+ // Pick a random node.
+ let idx = Int.random(in: 0..<neighbors.count)
+ var labels_to_counts: [Int: Double] = [:]
+ let end: Int = Int(neighbors[idx].index2)
+
+ for i in Int(neighbors[idx].index1)..<end {
+
+ labels_to_counts[labels[Int(edges[i].index2)], default: 0] += Double(edges[i].distance)
+ }
+
+ var bestScore: Double = -Double.infinity
+ var bestLabel = labels[idx]
+ let sorted_labels_to_counts = labels_to_counts.sorted { (a, b) -> Bool in
+ a.key < b.key
+ }
+ sorted_labels_to_counts.forEach { (i) in
+ if i.value > bestScore {
+ bestScore = i.value
+ bestLabel = i.key
+ }
+ }
+ labels[idx] = bestLabel
+ }
+ var label_remap: [Int: Int] = [:]
+ for (i, _) in labels.enumerated() {
+ let next_id = label_remap.count
+ if label_remap[labels[i]] == nil {
+ label_remap[labels[i]] = next_id
+ }
+ }
+
+ for (i, _) in labels.enumerated() {
+ labels[i] = label_remap[labels[i]] ?? 0
+ }
+ return labels
+ }
+
+ func group<T>(objects: [T], labels: [Int]) -> [[T]] {
+ var cluster: [Int : [T]] = [:]
+ for (i, value) in labels.enumerated() {
+ if cluster[value] != nil {
+ cluster[value]!.append(objects[i])
+ }else {
+ cluster[value] = [objects[i]]
+ }
+ }
+ return cluster.map { (_ , value) -> [T] in
+ value
+ }
+ }
+}
+
+
+
+
+let a = 1.1
+let b = 1.2
+let c = 1.3
+let d = 4.0
+
+let chineseWhispers = ChineseWhispers()
+let labels = chineseWhispers.chinese_whispers(objects: [a, b, c, d], distanceFunction: { (a, b) -> Double in
+ abs(a-b)
+}, eps: 0.4, numIterations: 100)
+let group = chineseWhispers.group(objects: [a, b, c, d], labels: labels)
diff --git a/Chinese Whisper/ChineseWhisper.swift b/Chinese Whisper/ChineseWhisper.swift
new file mode 100644
index 000000000..6531adcf7
--- /dev/null
+++ b/Chinese Whisper/ChineseWhisper.swift
@@ -0,0 +1,196 @@
+//
+// ChineseWhisper.swift
+//
+//
+// Created by Amir Lahav on 15/02/2021.
+//
+
+import Foundation
+
+struct SamplePair {
+
+ let index1: Int
+ let index2: Int
+ let distance: Double
+
+ init(idx1: Int, idx2: Int, distance: Double = 1) {
+ self.distance = distance
+ if (idx1 < idx2) {
+ index1 = idx1
+ index2 = idx2
+ } else {
+ index1 = idx2
+ index2 = idx1
+ }
+ }
+}
+
+struct OrderedSamplePair {
+
+ let index1: Int
+ let index2: Int
+ let distance: Double
+
+ init(idx1: Int, idx2: Int, distance: Double = 1) {
+ self.distance = distance
+ index1 = idx1
+ index2 = idx2
+ }
+}
+
+struct Pair {
+ let index1: Int
+ let index2: Int
+
+ init(idx1: Int, idx2: Int) {
+ index1 = idx1
+ index2 = idx2
+ }
+}
+
+class ChineseWhispers {
+
+ func convertUnorderedToOrdered(edges: [SamplePair]) -> [OrderedSamplePair] {
+ var orderdPairs: [OrderedSamplePair] = []
+ orderdPairs.reserveCapacity(edges.count*2)
+
+ for (i, _) in edges.enumerated() {
+ orderdPairs.append(OrderedSamplePair(idx1: edges[i].index1, idx2: edges[i].index2, distance: edges[i].distance))
+ if edges[i].index1 != edges[i].index2 {
+ orderdPairs.append(OrderedSamplePair(idx1: edges[i].index2, idx2: edges[i].index1, distance: edges[i].distance))
+ }
+ }
+ return orderdPairs.sorted { (a, b) -> Bool in
+ a.index1 < b.index1 || (a.index1 == b.index1 && a.index2 < b.index2)
+ }
+ }
+
+ func findNeighborRanges(edges: [OrderedSamplePair]) -> [Pair] {
+ let numNodes: Int = maxIndexPlusOne(pairs: edges)
+ var neighbors: [Pair] = Array(repeating: Pair(idx1: 0, idx2: 0), count: Int(numNodes))
+ var cur_node: Int = 0
+ var start_idx: Int = 0
+
+ for (index, value) in edges.enumerated() {
+ if value.index1 != cur_node {
+ neighbors[Int(cur_node)] = Pair(idx1: start_idx,
+ idx2: index)
+ start_idx = index
+ cur_node = value.index1
+ }
+ }
+ if !neighbors.isEmpty {
+ neighbors[Int(cur_node)] = Pair(idx1: start_idx,
+ idx2: edges.count)
+ }
+ return neighbors
+ }
+
+ func maxIndexPlusOne(pairs: [OrderedSamplePair]) -> Int {
+ if pairs.count == 0 {
+ return 0
+ }else {
+ var max_idx: Int = 0
+ for (_, value) in pairs.enumerated() {
+ if value.index1 > max_idx {
+ max_idx = value.index1
+ }
+ if value.index2 > max_idx {
+ max_idx = value.index2
+ }
+ }
+ return max_idx + 1
+ }
+
+ }
+
+
+ func chinese_whispers<T>(
+ objects: [T],
+ distanceFunction: (T, T) -> Double,
+ eps: Double,
+ numIterations: Int) -> [Int] {
+ var edges: [SamplePair] = []
+ guard !objects.isEmpty else {
+ return []
+ }
+ for i in 0...objects.count-1 {
+ for j in i...objects.count-1 {
+ let length = distanceFunction(objects[i], objects[j])
+ if length < eps {
+ edges.append(SamplePair(idx1: i, idx2: j))
+ }
+ }
+ }
+ return chinese_whispers(edges: edges, numIterations: numIterations)
+ }
+
+ func chinese_whispers(
+ edges: [SamplePair],
+ numIterations: Int) -> [Int] {
+ let orderdEdges = convertUnorderedToOrdered(edges: edges)
+ return chinese_whispers(edges: orderdEdges, numIterations: numIterations)
+ }
+
+ func chinese_whispers(
+ edges: [OrderedSamplePair],
+ numIterations: Int) -> [Int] {
+ let neighbors = findNeighborRanges(edges: edges)
+ var labels: [Int] = Array<Int>(repeating: 0, count: neighbors.count)
+ for i in 0...neighbors.count-1 {
+ labels[i] = i
+ }
+
+ for _ in 0..<(neighbors.count * numIterations) {
+
+ // Pick a random node.
+ let idx = Int.random(in: 0..<neighbors.count)
+ var labels_to_counts: [Int: Double] = [:]
+ let end: Int = Int(neighbors[idx].index2)
+
+ for i in Int(neighbors[idx].index1)..<end {
+
+ labels_to_counts[labels[Int(edges[i].index2)], default: 0] += Double(edges[i].distance)
+ }
+
+ var bestScore: Double = -Double.infinity
+ var bestLabel = labels[idx]
+ let sorted_labels_to_counts = labels_to_counts.sorted { (a, b) -> Bool in
+ a.key < b.key
+ }
+ sorted_labels_to_counts.forEach { (i) in
+ if i.value > bestScore {
+ bestScore = i.value
+ bestLabel = i.key
+ }
+ }
+ labels[idx] = bestLabel
+ }
+ var label_remap: [Int: Int] = [:]
+ for (i, _) in labels.enumerated() {
+ let next_id = label_remap.count
+ if label_remap[labels[i]] == nil {
+ label_remap[labels[i]] = next_id
+ }
+ }
+
+ for (i, _) in labels.enumerated() {
+ labels[i] = label_remap[labels[i]] ?? 0
+ }
+ return labels
+ }
+
+ func group<T>(objects: [T], labels: [Int]) -> [[T]] {
+ var cluster: [Int : [T]] = [:]
+ for (i, value) in labels.enumerated() {
+ if cluster[value] != nil {
+ cluster[value]!.append(objects[i])
+ }else {
+ cluster[value] = [objects[i]]
+ }
+ }
+ return cluster.map { (_ , value) -> [T] in
+ value
+ }
+ }
+}