Code Refactoring

Modifying the merge method in Merge Sort:
* empty array definition.
* unifying the while loop.

Author: yossan

Merge Sort/MergeSort.playground/Contents.swift

@@ -21,31 +21,24 @@ func merge<T: Comparable>(leftPile: [T], rightPile: [T]) -> [T] {
     orderedPile.reserveCapacity(leftPile.count + rightPile.count)
   }
 
-  while leftIndex < leftPile.count && rightIndex < rightPile.count {
+  while true {
+    guard leftIndex < leftPile.endIndex else {
+      orderedPile.append(contentsOf: rightPile[rightIndex..<rightPile.endIndex])
+      break
+    }
+    guard rightIndex < rightPile.endIndex else {
+      orderedPile.append(contentsOf: leftPile[leftIndex..<leftPile.endIndex])
+      break
+    }
+    
     if leftPile[leftIndex] < rightPile[rightIndex] {
       orderedPile.append(leftPile[leftIndex])
       leftIndex += 1
-    } else if leftPile[leftIndex] > rightPile[rightIndex] {
-      orderedPile.append(rightPile[rightIndex])
-      rightIndex += 1
     } else {
-      orderedPile.append(leftPile[leftIndex])
-      leftIndex += 1
       orderedPile.append(rightPile[rightIndex])
       rightIndex += 1
     }
   }
-
-  while leftIndex < leftPile.count {
-    orderedPile.append(leftPile[leftIndex])
-    leftIndex += 1
-  }
-
-  while rightIndex < rightPile.count {
-    orderedPile.append(rightPile[rightIndex])
-    rightIndex += 1
-  }
-
   return orderedPile
 }
 

Merge Sort/MergeSort.swift

@@ -17,35 +17,30 @@ func mergeSort<T: Comparable>(_ array: [T]) -> [T] {
 func merge<T: Comparable>(leftPile: [T], rightPile: [T]) -> [T] {
   var leftIndex = 0
   var rightIndex = 0
-  var orderedPile = [T]()
+  var orderedPile: [T] = []
   if orderedPile.capacity < leftPile.count + rightPile.count {
     orderedPile.reserveCapacity(leftPile.count + rightPile.count)
   }
 
-  while leftIndex < leftPile.count && rightIndex < rightPile.count {
-    if leftPile[leftIndex] < rightPile[rightIndex] {
-      orderedPile.append(leftPile[leftIndex])
-      leftIndex += 1
-    } else if leftPile[leftIndex] > rightPile[rightIndex] {
-      orderedPile.append(rightPile[rightIndex])
-      rightIndex += 1
-    } else {
-      orderedPile.append(leftPile[leftIndex])
-      leftIndex += 1
-      orderedPile.append(rightPile[rightIndex])
-      rightIndex += 1
-    }
-  }
-
-  while leftIndex < leftPile.count {
-    orderedPile.append(leftPile[leftIndex])
-    leftIndex += 1
+  while true {
+      guard leftIndex < leftPile.endIndex else {
+          orderedPile.append(contentsOf: rightPile[rightIndex..<rightPile.endIndex])
+          break
+      }
+      guard rightIndex < rightPile.endIndex else {
+          orderedPile.append(contentsOf: leftPile[leftIndex..<leftPile.endIndex])
+          break
+      }
+      
+      if leftPile[leftIndex] < rightPile[rightIndex] {
+          orderedPile.append(leftPile[leftIndex])
+          leftIndex += 1
+      } else {
+          orderedPile.append(rightPile[rightIndex])
+          rightIndex += 1
+      }
   }
 
-  while rightIndex < rightPile.count {
-    orderedPile.append(rightPile[rightIndex])
-    rightIndex += 1
-  }
 
   return orderedPile
 }