189. Rotate Array

Author: Partho Biswas

README.md

@@ -190,6 +190,7 @@ I have solved quite a number of problems from several topics. See the below tabl
 |76| **[896. Monotonic Array](https://tinyurl.com/y8a95fb6)** | [Python](https://tinyurl.com/wu6rdaw/896_Monotonic_Array.py), [Swift](https://tinyurl.com/wuja3c4/896_Monotonic_Array.swift) | --- | Eassy |  |
 |77| **[670. Maximum Swap](https://tinyurl.com/y2zhdd33)** | [Python](https://tinyurl.com/wu6rdaw/670_Maximum_Swap.py), [Swift](https://tinyurl.com/wuja3c4/670_Maximum_Swap.swift) | [Art 1](https://tinyurl.com/y8vqklj3) | Medium |  |
 |78| **[825. Friends Of Appropriate Ages](https://tinyurl.com/ycgnqxb8)** | [Python](https://tinyurl.com/wu6rdaw/825_Friends_Of_Appropriate_Ages.py), [Swift](https://tinyurl.com/wuja3c4/825_Friends_Of_Appropriate_Ages.swift) | [Art 1](https://tinyurl.com/yd4oal3l) | Medium | Think differently from a different angle. Loved this problem |
+|79| **[189. Rotate Array](https://tinyurl.com/yalocp9r)** | [Python](https://tinyurl.com/wu6rdaw/189_Rotate_Array.py), [Swift](https://tinyurl.com/wuja3c4/189_Rotate_Array.swift) | --- | Easy | Getting to inplace (O(n) time and O(1) space) solution is tricky. |
 
 
 </p>

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/189_Rotate_Array.swift

@@ -0,0 +1,44 @@
+import Foundation
+class Solution {
+    func rotate(_ nums: inout [Int], _ k: Int) {
+        var steps = k % nums.count
+        if steps == 0 {
+            return
+        }
+        nums.reverse()
+        
+        // Swap first portion
+        var (left, right) = (0, steps - 1)
+        while left < right {
+            nums.swapAt(left, right)
+            left += 1
+            right -= 1
+        }
+        
+        // Swap last portion
+        (left, right) = (steps, nums.count - 1)
+        while left < right {
+            nums.swapAt(left, right)
+            left += 1
+            right -= 1
+        }
+    }
+}
+
+/*
+ Input: nums = [1,2,3,4,5,6,7], k = 3
+ Output: [5,6,7,1,2,3,4]
+ 
+ 
+  1,2,3,4, 5,6,7
+ 
+  1,2,3,4, 7,6,5
+ 
+  7,6,5, 4,3,2,1
+ 
+ 
+ 
+ >5,6,7, 1,2,3,4
+ 
+ >5,6,7,1,2,3,4
+*/