A sorting algorithm that slightly improves on selection sort?

CServer Side ProgrammingProgramming

Here we will see some improvements on selection sort. As we know that the selection sort works by taking either the minimum or maximum element from the array and place that element at correct position. In this approach, we want to sort the array in both ways. Here we will take the max and min simultaneously, then sort the array from two end. Let us see the algorithm to get better idea.

Algorithm

twoWaySelectionSort(arr, n)

begin
   for i := 0, and j := n-1, increase i by 1, and decrease j by 1, until i>=j, do
      min := minimum element from index i to j
      max := maximum element from index i to j
      i_min := index of min
      i_max := index of max
      exchange the arr[i] and arr[i_min]
      if arr[i_min] is same as max, then
         swap arr[j] and arr[i_min]
      else
         swap arr[j] and arr[i_max]
      end if
   done
end

Example

 Live Demo

#include<iostream>
using namespace std;
void twoWaySelectionSort(int arr[], int n) {
   //i will move from left, and j will move from right
   for (int i = 0, j = n - 1; i < j; i++, j--) {
      int min = arr[i], max = arr[i];
      int i_min = i, i_max = i; //i_min and i_max will hold min and max index respectively
      for (int k = i; k <= j; k++) {
         if (arr[k] > max) {
            max = arr[k];
            i_max = k;
         } else if (arr[k] < min) {
            min = arr[k];
            i_min = k;
         }
      }
      swap(arr[i], arr[i_min]); //put the min into the index i
      if (arr[i_min] == max)
         swap(arr[j], arr[i_min]);
      else
         swap(arr[j], arr[i_max]);
   }
}
main() {
   int arr[] = { 25, 45, 14, 10, 23, 29, 65, 21, 78, 96, 30 };
   int n = sizeof(arr) / sizeof(arr[0]);
   twoWaySelectionSort(arr, n);
   cout << "Sorted array: ";
   for (int i = 0; i < n; i++)
   cout << arr[i] << " ";
}

Output

Sorted array: 10 14 21 23 25 29 30 45 65 78 96
raja
Published on 26-Jul-2019 06:31:21
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