Swift Implementation for LCCI 10.10 (#2716)

Author: klever34

lcci/10.10.Rank from Stream/README.md

@@ -275,6 +275,52 @@ class StreamRank {
  */
 ```
 
+```swift
+class BinaryIndexedTree {
+    private var n: Int
+    private var c: [Int]
+
+    init(_ n: Int) {
+        self.n = n
+        self.c = Array(repeating: 0, count: n + 1)
+    }
+
+    func update(_ x: Int, _ delta: Int) {
+        var idx = x
+        while idx <= n {
+            c[idx] += delta
+            idx += (idx & -idx)
+        }
+    }
+
+    func query(_ x: Int) -> Int {
+        var sum = 0
+        var idx = x
+        while idx > 0 {
+            sum += c[idx]
+            idx -= (idx & -idx)
+        }
+        return sum
+    }
+}
+
+class StreamRank {
+    private var tree: BinaryIndexedTree
+
+    init() {
+        tree = BinaryIndexedTree(50010)
+    }
+
+    func track(_ x: Int) {
+        tree.update(x + 1, 1)
+    }
+
+    func getRankOfNumber(_ x: Int) -> Int {
+        return tree.query(x + 1)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/10.10.Rank from Stream/README_EN.md

@@ -277,6 +277,52 @@ class StreamRank {
  */
 ```
 
+```swift
+class BinaryIndexedTree {
+    private var n: Int
+    private var c: [Int]
+
+    init(_ n: Int) {
+        self.n = n
+        self.c = Array(repeating: 0, count: n + 1)
+    }
+
+    func update(_ x: Int, _ delta: Int) {
+        var idx = x
+        while idx <= n {
+            c[idx] += delta
+            idx += (idx & -idx)
+        }
+    }
+
+    func query(_ x: Int) -> Int {
+        var sum = 0
+        var idx = x
+        while idx > 0 {
+            sum += c[idx]
+            idx -= (idx & -idx)
+        }
+        return sum
+    }
+}
+
+class StreamRank {
+    private var tree: BinaryIndexedTree
+
+    init() {
+        tree = BinaryIndexedTree(50010)
+    }
+
+    func track(_ x: Int) {
+        tree.update(x + 1, 1)
+    }
+
+    func getRankOfNumber(_ x: Int) -> Int {
+        return tree.query(x + 1)
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/10.10.Rank from Stream/Solution.swift

@@ -0,0 +1,45 @@
+
+class BinaryIndexedTree {
+    private var n: Int
+    private var c: [Int]
+
+    init(_ n: Int) {
+        self.n = n
+        self.c = Array(repeating: 0, count: n + 1)
+    }
+
+    func update(_ x: Int, _ delta: Int) {
+        var idx = x
+        while idx <= n {
+            c[idx] += delta
+            idx += (idx & -idx)
+        }
+    }
+
+    func query(_ x: Int) -> Int {
+        var sum = 0
+        var idx = x
+        while idx > 0 {
+            sum += c[idx]
+            idx -= (idx & -idx)
+        }
+        return sum
+    }
+}
+
+class StreamRank {
+    private var tree: BinaryIndexedTree
+
+    init() {
+        tree = BinaryIndexedTree(50010)
+    }
+
+    func track(_ x: Int) {
+        tree.update(x + 1, 1)
+    }
+
+    func getRankOfNumber(_ x: Int) -> Int {
+        return tree.query(x + 1)
+    }
+}
+