Merge pull request tulika-99#58 from monil/bubblesort-scala

Bubble Sort implementation in Scala

Author: tulika-99

Bubble Sort/BubbleSortScala/Bubble Sort algo.txt

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+Bubble Sort
+
+Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in wrong order.
+Example:
+First Pass:
+( 5 1 4 2 8 ) �> ( 1 5 4 2 8 ), Here, algorithm compares the first two elements, and swaps since 5 > 1.
+( 1 5 4 2 8 ) �>  ( 1 4 5 2 8 ), Swap since 5 > 4
+( 1 4 5 2 8 ) �>  ( 1 4 2 5 8 ), Swap since 5 > 2
+( 1 4 2 5 8 ) �> ( 1 4 2 5 8 ), Now, since these elements are already in order (8 > 5), algorithm does not swap them.
+Second Pass:
+( 1 4 2 5 8 ) �> ( 1 4 2 5 8 )
+( 1 4 2 5 8 ) �> ( 1 2 4 5 8 ), Swap since 4 > 2
+( 1 2 4 5 8 ) �> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) �>  ( 1 2 4 5 8 )
+Now, the array is already sorted, but our algorithm does not know if it is completed. The algorithm needs one whole pass without any swap to know it is sorted.
+Third Pass:
+( 1 2 4 5 8 ) �> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) �> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) �> ( 1 2 4 5 8 )
+( 1 2 4 5 8 ) �> ( 1 2 4 5 8 )

Bubble Sort/BubbleSortScala/BubbleSort.scala

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+/**
+  *
+  * Bubble sort implemented in a functional way i.e. Scala Style.
+  * Scala encourages to implement solutions in recursive way.
+  * It also gives flexibility of implementing solution in iterative way,
+  * but pure scala style is in functional way.
+  *
+  */
+object BubbleSort {
+
+  def bubbleSort(array: List[Int]) : List[Int] = {
+
+    def sort(pendingList: List[Int], sortedList: List[Int]) : List[Int] = {
+      if(pendingList.isEmpty)
+        sortedList
+      else
+        bubble(pendingList,Nil, sortedList)
+    }
+
+    def bubble(pendingList: List[Int] , tempList: List[Int], sortedList: List[Int]) : List[Int] = {
+      pendingList match {
+        case h1 :: h2 :: t => {
+          if(h1 > h2) bubble(h1 :: t, h2 :: tempList, sortedList)
+          else bubble(h2 :: t, h1 :: tempList, sortedList)
+        }
+        case h1 :: Nil => sort(tempList, h1 :: sortedList)
+      }
+    }
+
+    sort(array, Nil)
+
+  }
+
+
+  def main(args: Array[String]): Unit = {
+    val x = bubbleSort(List(1,5,3,4,2))
+    print(x)
+  }
+
+
+}
+