Function to sort an array using insertion sort

Insertion sort is slightly better sorting method among O(n2) algorithms. It is effecient if the elements are almost sorted and if the size is small.

Insertion sort basically works by splitting your elements into two parts. Sorted half and unsorted half. To begin with, Sorted half is empty and unsorted half has all elements. Then one element is removed from unsorted half and added to the sorted half. When adding , this element is inserted at the correct location. This process is continued till we have all the elements in sorted half and unsorted half is empty. Now let us try to understand it with a diagram.

First 17 is removed from unsorted array and added to sorted array. Since there is one element there, it is sorted. Next 4 which is front most element now in unsored array is removed and added to sorted array. But 4 is smaller than 17, so 17 is pushed to right and its place is taken by 4.
   Next 32 is removed from the front of unsorted array and added to sorted array. But here in sorted array to last element 17 is smaller. So 32 is in its correct place. Next 1 is moved from front of unsorted array. In sorted array, 32 is larger and pushed to right. Next 17 is pushed to right and 4 is also pushed to right. Now 1 is placed in 4's position. As you can see, now these 4 elements are sorted. This process continues until all the elements are removed from unsorted array.
   Removing front most element from the array takes O(1) X N elements. And inserting an element takes in worst case O(N) time. Hence complexity is O(N² ) .
C++ function to insertion sort an array is really very simple and small.

#include<iostream> using std::cin; using std::cout; void insertionSort(int *arr,int size); void printArray(int *arr,int size); int main() {     int n;     cout<<"Size of array:";     cin>>n;     int a[n];     cout<<"Elements of array:";     for(int i=0;i<size;i++)          cin>>a[i];      insertionSort(a,n);      printArray(a,n);      return 0; }

void insertionSort(int *arr,int size) {    for(int i=1;i<size;i++)    {         int val = arr[i];         int j;         for(j=i-1;j>=0 && arr[j] >val;j--)         {                  arr[j+1]=arr[j];          }          arr[j+1]=val;    } } void printArray(int *arr,int size) {      for(int i=0;i<size;i++)              cout<< arr[i]<<"=====";    }

In the insertionSort function, outer loop is for extracting one element from unsorted array. And inner loop is for inserting it in the sorted array and pushing elements to right as needed.
Writing insertion sort for linked list is much simple as well. You take one more linked list - sortedList. Now remove front element from list and insert it in ascending order in sortedList.