C++ Program to Implement Insertion Sort

This sorting technique is similar with the card sorting technique, in other words we sort cards using insertion sort mechanism. For this technique, we pick up one element from the data set and shift the data elements to make a place to insert back the picked up element into the data set.

The complexity of Insertion Sort Technique

• Time Complexity: O(n) for best case, O(n2) for average and worst case

• Space Complexity: O(1)

Input − The unsorted list: 9 45 23 71 80 55
Output − Array after Sorting: 9 23 45 55 71 80

Algorithm

insertionSort(array, size)

Input: An array of data, and the total number in the array

Output: The sorted Array

Begin
   for i := 1 to size-1 do
      key := array[i]
      j := i
      while j > 0 AND array[j-1] > key do
         array[j] := array[j-1];
         j := j – 1
      done
      array[j] := key
   done
End

Example Code

#include<iostream>
using namespace std;
void display(int *array, int size) {
   for(int i = 0; i<size; i++)
      cout << array[i] << " ";
   cout << endl;
}
void insertionSort(int *array, int size) {
   int key, j;
   for(int i = 1; i<size; i++) {
      key = array[i];//take value
      j = i;
      while(j > 0 && array[j-1]>key) {
         array[j] = array[j-1];
         j--;
      }
      array[j] = key;   //insert in right place
   }
}
int main() {
   int n;
   cout << "Enter the number of elements: ";
   cin >> n;
   int arr[n];    //create an array with given number of elements
   cout << "Enter elements:" << endl;
   for(int i = 0; i<n; i++) {
      cin >> arr[i];
   }
   cout << "Array before Sorting: ";
   display(arr, n);
   insertionSort(arr, n);
   cout << "Array after Sorting: ";
   display(arr, n);
}

Output

Enter the number of elements: 6
Enter elements:
9 45 23 71 80 55
Array before Sorting: 9 45 23 71 80 55
Array after Sorting: 9 23 45 55 71 80