2007_Find_Original_Array_From_Doubled_Array

Author: partho-maple

README.md

@@ -260,6 +260,7 @@ I have solved quite a number of problems from several topics. See the below tabl
 |46| **[722. Remove Comments](https://tinyurl.com/y288v3lv)** | [Python](https://tinyurl.com/wu6rdaw/722_Remove_Comments.py), [Swift](https://tinyurl.com/wuja3c4/722_Remove_Comments.swift) | [Art 1](https://tinyurl.com/y56j4p76) | Medium | |
 |47| **[443. String Compression](https://tinyurl.com/ybll48vn)** | [Python](https://tinyurl.com/wu6rdaw/443_String_Compression.py), [Swift](https://tinyurl.com/wuja3c4/443_String_Compression.swift) | [Art 1](https://tinyurl.com/y5knbkcd) | Medium | |
 |48| **[1525_Number_of_Good_Ways_to_Split_a_String](https://tinyurl.com/yzree7us)** | [Swift](https://tinyurl.com/wuja3c4/1525_Number_of_Good_Ways_to_Split_a_String.swift) | --- | Medium | |
+|48| **[2007_Find_Original_Array_From_Doubled_Array](https://tinyurl.com/yhnzl82h)** | [Swift](https://tinyurl.com/wuja3c4/2007_Find_Original_Array_From_Doubled_Array.swift) | --- | Medium | |
 
 
 </p>

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/2007_Find_Original_Array_From_Doubled_Array.swift

@@ -0,0 +1,32 @@
+import Foundation
+class Solution {
+ func findOriginalArray(_ changed: [Int]) -> [Int] {
+ guard changed.count % 2 == 0 else { return [] }
+ let changedSorted = changed.sorted()
+ var countMap = [Int:Int]()
+ changed.forEach { item in
+ countMap[item, default: 0] += 1
+ }
+ var original = [Int]()
+ for item in changedSorted {
+ let key = item * 2
+ if let _ = countMap[key],
+ let _ = countMap[item] {
+ countMap[key]! -= 1
+ countMap[item]! -= 1
+ original.append(item)
+ if let count = countMap[key], count == 0 {
+ countMap.removeValue(forKey:key)
+ }
+ if let count = countMap[item], count == 0 {
+ countMap.removeValue(forKey:item)
+ }
+ }
+ }
+ if countMap.keys.count == 0 && original.count * 2 == changed.count {
+ return original
+ } else {
+ return []
+ }
+ }
+}