Insertion Sort

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.

insertion sort
Figure of Sorting Technique

Implementation of Insertion Sort

Program Code in C :-


//function to print array
void printarray(int arr[], int n)
  for(int i=0; i<n; i++)
    printf("%d ",arr[i]);

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];
    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 75Code language: PHP (php)

Time and Space Complexity of Insertion Sort

Time Complexity
Worst CaseO(n2)
Best CaseO(n)
Average CaseO(n2)
Space Complexity
Worst CaseO(n2) total
O(1) auxiliary

Advantages of Insertion Sort

  1. Simple implementation.
  2. Efficient for small data.
  3. Stable: Maintains relative order of input data if the keys are the same.
  4. In-place requires only a constant amount O(1) of additional memory space.

Other Sorting Algorithms:-

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