feat: add swift implementation to lcci problem: No.17.18 (doocs#2805)

Author: klever34

lcci/17.18.Shortest Supersequence/README.md

@@ -187,6 +187,50 @@ function shortestSeq(big: number[], small: number[]): number[] {
 }
 ```
 
+```swift
+class Solution {
+    func shortestSeq(_ big: [Int], _ small: [Int]) -> [Int] {
+        let needCount = small.count
+        var need = [Int: Int]()
+        var window = [Int: Int]()
+        small.forEach { need[$0, default: 0] += 1 }
+        
+        var count = needCount
+        var minLength = Int.max
+        var result = (-1, -1)
+        
+        var left = 0
+        for right in 0..<big.count {
+            let element = big[right]
+            if need[element] != nil {
+                window[element, default: 0] += 1
+                if window[element]! <= need[element]! {
+                    count -= 1
+                }
+            }
+            
+            while count == 0 {
+                if right - left + 1 < minLength {
+                    minLength = right - left + 1
+                    result = (left, right)
+                }
+                
+                let leftElement = big[left]
+                if need[leftElement] != nil {
+                    window[leftElement]! -= 1
+                    if window[leftElement]! < need[leftElement]! {
+                        count += 1
+                    }
+                }
+                left += 1
+            }
+        }
+        
+        return result.0 == -1 ? [] : [result.0, result.1]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/17.18.Shortest Supersequence/README_EN.md

@@ -191,6 +191,50 @@ function shortestSeq(big: number[], small: number[]): number[] {
 }
 ```
 
+```swift
+class Solution {
+    func shortestSeq(_ big: [Int], _ small: [Int]) -> [Int] {
+        let needCount = small.count
+        var need = [Int: Int]()
+        var window = [Int: Int]()
+        small.forEach { need[$0, default: 0] += 1 }
+        
+        var count = needCount
+        var minLength = Int.max
+        var result = (-1, -1)
+        
+        var left = 0
+        for right in 0..<big.count {
+            let element = big[right]
+            if need[element] != nil {
+                window[element, default: 0] += 1
+                if window[element]! <= need[element]! {
+                    count -= 1
+                }
+            }
+            
+            while count == 0 {
+                if right - left + 1 < minLength {
+                    minLength = right - left + 1
+                    result = (left, right)
+                }
+                
+                let leftElement = big[left]
+                if need[leftElement] != nil {
+                    window[leftElement]! -= 1
+                    if window[leftElement]! < need[leftElement]! {
+                        count += 1
+                    }
+                }
+                left += 1
+            }
+        }
+        
+        return result.0 == -1 ? [] : [result.0, result.1]
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/17.18.Shortest Supersequence/Solution.swift

@@ -0,0 +1,41 @@
+class Solution {
+    func shortestSeq(_ big: [Int], _ small: [Int]) -> [Int] {
+        let needCount = small.count
+        var need = [Int: Int]()
+        var window = [Int: Int]()
+        small.forEach { need[$0, default: 0] += 1 }
+        
+        var count = needCount
+        var minLength = Int.max
+        var result = (-1, -1)
+        
+        var left = 0
+        for right in 0..<big.count {
+            let element = big[right]
+            if need[element] != nil {
+                window[element, default: 0] += 1
+                if window[element]! <= need[element]! {
+                    count -= 1
+                }
+            }
+            
+            while count == 0 {
+                if right - left + 1 < minLength {
+                    minLength = right - left + 1
+                    result = (left, right)
+                }
+                
+                let leftElement = big[left]
+                if need[leftElement] != nil {
+                    window[leftElement]! -= 1
+                    if window[leftElement]! < need[leftElement]! {
+                        count += 1
+                    }
+                }
+                left += 1
+            }
+        }
+        
+        return result.0 == -1 ? [] : [result.0, result.1]
+    }
+}