Insertion sort is a simple sorting algorithm that works similar to the way you sort playing cards in your hands. The array is virtually split into a sorted and an unsorted part. Values from the unsorted part are picked and placed at the correct position in the sorted part.
Algorithm
To sort an array of size n in ascending order:
1: Iterate from arr[1] to arr[n] over the array.
2: Compare the current element (key) to its predecessor.
3: If the key element is smaller than its predecessor, compare it to the elements before. Move the greater elements one position up to make space for the swapped element.
// 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[] = { 12, 11, 13, 5, 6 };
int n = sizeof(arr) / sizeof(arr[0]);
insertionSort(arr, n);
printArray(arr, n);
return 0;
}
