# Insertion Sort

It is an simple sorting algorithm that builds the final sorted array(or array) one at a time. Here, a sub-lists is maintained which is always sorted. It is much less efficient on large lists than more advanced algorithms such as quick sort, heap sort or merge sort. Example: 9, 8, 10, 5, 6 Let us loop for i = 1 (second element of the array) to 4 (last element of the array) i = 1. Since 8 is smaller than 9, move 9 and insert 8 before 9

8, 9, 10, 5, 6 i = 2. 10 will remain at its position as all elements in A[0..I-1] are smaller than 10

8, 9, 10, 5, 6 i = 3. 5 will move to the beginning and all other elements from 8 to 10 will move one position ahead of their current position.

5, 8, 9, 10, 6 i = 4. 6 will move to position after 5, and elements from 8 to 10 will move one position ahead of their current position.

5, 6, 8, 9, 10 Another Example: Here is an visual example of insertion sort. Implementation in C: // C program for insertion sort

#include <math.h>

#include <stdio.h>

// Function to sort an array using insertion sort

void insertionSort(int arr[], int n)

{

int i, key, j;

for (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 = j - 1;

}

arr[j + 1] = key;

}

}

// A utility function to print an array of size n

void printArray(int arr[], int n)

{

int i;

for (i = 0; i < n; i++)

printf("%d ", arr[i]);

printf("\n");

}

/* Driver program to test insertion sort */

int main()

{

int arr[] = { 9, 8, 10, 5, 6 };

int n = sizeof(arr) / sizeof(arr[0]);

insertionSort(arr, n);

printArray(arr, n);

return 0;

} Output: 5 6 8 9 10 Miscellaneous: Time Complexity: O(n*2). Learn more about time complexity here. In-place: Yes Stable: Yes