Q:

Array Rotation in Scala

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YasminRadwan26
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2022-07-06
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Array rotation is the process of shifting elements of the array in a specific direction and rotate the last element to first or first to last based on the direction of rotation of the array.

There are two types of array rotation:

  1. Lift Shift: Leftward shifting of elements from index n to n-1, and shift element at the first index to the last index.
  2. Right Shift: Rightward shifting of elements from index n-1 to n, and shift element at last index to the first index.

Example:

    Array: {2, 5, 7, 9, 1, 3}
    Left shifted array: {5, 7, 9, 1, 3, 2}
    Right shifted array: {3, 2, 5, 7, 9, 1}

Now, to left rotate array by n elements, we will first store the last element of the array in a temporary variable. And run a loop from last to first. And copy element at the n-1 position to n and so on.

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YasminRadwan26
2022-07-06
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Program:

object MyClass {
    def rotateArray(A: Array[Int], K: Int): Array[Int] = {
        if (A.isEmpty) A
        else rotate(A.toList, K).toArray
    }
    
    def rotateStepwise(l: List[Int]) = {
        l.take(l.size - 1).+:(l.last)
    }
    
    def rotate(l: List[Int], K: Int): List[Int] = {
      if (K == 0) l
      else rotate(rotateStepwise(l), K - 1)
    }
    
    def main(args: Array[String]) {
        var arr = Array(1, 5, 6, 8, 12, 7)
        print("Initial Array : ")
        for(i <- 0 to arr.length-1){
            print(arr(i)+" ")
        }
        println()
        var a = rotateArray(arr, 1)
        print("Array after right rotation : ")
        for(i <- 0 to a.length-1){
            print(a(i)+" ")
        }
    }
}

Output

Initial Array : 1 5 6 8 12 7 
Array after right rotation : 7 1 5 6 8 12

Explanation:

In this above code, we have a function that is used to right rotate an array by k steps. The function calls another function which does the rotation work. The function calls a function to rotate the array single step k times.  

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