[Sort] Add solution to Sort Transformed Array

Author: Yi Gu

Sort/SortTransformedArray.swift

@@ -0,0 +1,46 @@
+/**
+ * Question Link: https://leetcode.com/problems/sort-transformed-array/
+ * Primary idea: Compare head and tail and put larger/smaller one to end/start of array,
+ *               according to a is less than 0 or not
+ * Time Complexity: O(n), Space Complexity: O(1)
+ */
+
+class SortTransformedArray {
+    func sortTransformedArray(_ nums: [Int], _ a: Int, _ b: Int, _ c: Int) -> [Int] {
+        var res = [Int](repeating: 0, count: nums.count)
+        var left = 0
+        var right = res.count - 1
+        var index = a >= 0 ? nums.count - 1 : 0
+        
+        while left <= right {
+            let leftVal = getRes(a, b, c, nums[left])
+            let rightVal = getRes(a, b, c, nums[right])
+            
+            if a >= 0 {
+                if leftVal > rightVal {
+                    res[index] = leftVal
+                    left += 1
+                } else {
+                    res[index] = rightVal
+                    right -= 1
+                }
+                index -= 1
+            } else if a < 0 {
+                if leftVal < rightVal {
+                    res[index] = leftVal
+                    left += 1
+                } else {
+                    res[index] = rightVal
+                    right -= 1
+                }
+                index += 1
+            }
+        }
+        
+        return res
+    }
+    
+    private func getRes(_ a: Int, _ b: Int, _ c: Int, _ x: Int) -> Int {
+        return a * x * x + b * x + c
+    }
+}