Here, We will learn about insertion sort in C, their algorithm, implementation code in C, time and space complexity and advantages..
What is Insertion sort?
Insertion Sort is a simple and efficient comparison sort. It works similarly as we sort cards in our hand in a card game.
The algorithm based on the idea that places an unsorted element at its suitable place in each iteration.
This sort algorithm with expensive runtime with O(n2).
Insertion Sort Algorithm
Every repetition of this sort removes an element from the input data and inserts it into the correct position in the already-sorted list until no input elements remain.

Implementation of Insertion Sort
Program Code in C :-
#include<stdio.h>
//function to print array
void printarray(int arr[], int n)
{
for(int i=0; i<n; i++)
{
printf("%d ",arr[i]);
}
printf("\n");
}
void insertionSort(int arr[], int n)
{
for(int i=0; i<n; i++)
{
int k = arr[i];
int j = i-1;
//compare key with each element on the left of it until an element
//smaller than it is found.
while(k < arr[j] && j >=0)
{
arr[j+1] = arr[j];
j--;
}
arr[j+1] = k;
}
}
//Driver code
int main()
{
int data[] = {4, 75, 74, 2, 54};
int n = sizeof(data) / sizeof(data[0]);
insertionSort(data, n);
printf("Sorted array : ");
printarray(data, n);
}
Code language: C++ (cpp)
Output :-
Sorted array : 2 4 54 74 75
Code language: PHP (php)
Time and Space Complexity of Insertion Sort
Time Complexity | |
Worst Case | O(n2) |
Best Case | O(n) |
Average Case | O(n2) |
Space Complexity | |
Worst Case | O(n2) total O(1) auxiliary |
Advantages of Insertion Sort
- Simple implementation.
- Efficient for small data.
- Stable: Maintains relative order of input data if the keys are the same.
- In-place requires only a constant amount O(1) of additional memory space.
Other Sorting Algorithms:-
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Counting Sort
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Bucket Sort
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Selection Sort
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Radix Sort
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Shell Sort
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Bubble Sort
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