Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. However, insertion sort provides several advantages: Simple implementation: Jon Bentley shows a three-line c version, and a five-line optimized version Efficient for (quite) small data sets, much like other quadratic sorting algorithmsAdaptive, i.e., efficient for data sets that are already substantially sorted: the time complexity is O(kn) when each component in the input is no more than K places away from its sorted position Stable; i.e., makes not change the relative order of components with equal keys

To perform an insertion sort, begin at the left-most component of the array and invoke insert to insert each component encountered into its correct position. It operates by beginning at the end of the sequence and shifting each component one place to the right until a suitable position is found for the new component.

```
//
// C++ implementation of insertion sort
//
// The All ▲lgorithms Project
//
// https://allalgorithms.com/sorting
// https://github.com/allalgorithms/cpp
//
// Contributed by: Andres Langberg
// Github: Unknown
//
#include <iostream>
/* Function to sort an array using insertion sort*/
void insertion_sort(int arr[], int n)
{
int key;
size_t j;
for (size_t i = 1; i < n; i++)
{
key = arr[i];
j = i - 1;
/* Move elements of arr[0..i-1], that are
greater than key, to one position ahead
of their current position */
while (j >= 0 && arr[j] > key)
{
arr[j + 1] = arr[j];
j--;
}
arr[j + 1] = key;
}
}
// A utility function to print an array of size n
void print_array(int arr[], int n)
{
for (size_t i = 0; i < n; i++)
{
std::cout << arr[i] << " ";
}
std::cout << std::endl;
}
/* Driver program to test insertion sort */
int main()
{
int arr[] = {12, 11, 13, 5, 6};
size_t n = sizeof(arr) / sizeof(arr[0]);
std::cout << "Unsorted array:" << std::endl;
print_array(arr, n);
insertion_sort(arr, n);
std::cout << "Sorted array:" << std::endl;
print_array(arr, n);
return 0;
}
```