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How does the Insertion Sort in DataStructures works?

2 min 56 sec read

Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort.

How does the Insertion Sort work?

Suppose we have an array in unsorted order (4,6,3,1)

1) In the first step, 6 will be compared with 4. Since 4 < 6 , no insertion takes place.

 

 

2) In the second step, 3 will be compared with 6. Since 3 < 6 , it must be on the left of 6 . Now on left of 6 , 4 is present so 3 will be compared with 4. Since 3 < 4, 3 must be on the left of 4. As there are no more elements present to the left of 4 , 3 will be inserted before 4.

 

 

Array will look loke this => 3,4,6,1.

 

 

3) In the third step, 1 will be compared with 6. Since 1 < 6 , it must be on the left of 6 . Now on left of 6 , 4 is present so 1 will be compared with 4. Since 1 < 4, 1 must be on the left of 4. Now on left of 4 , 3 is present so 1 will be compared with 3. Since 1 < 3, 1 must be on the left of 3. As there are no more elements present to the left of 3 , 1 will be inserted before 3.

 

 

Array will look loke this => 1,3,4,6.

 

 

Insertion Program in C:-

This basic Insertion Sort in C programming explains the concept of how to sort the elements using Insertion sort in Data Structures.

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <assert.h>


void insertionSort(int N, int arr[]) {
    int i,j;
    int value;
    for(i=1;i=0 && value<arr[j])
        {
            arr[j+1]=arr[j];
            j=j-1;
        }
        arr[j+1]=value;

        for (j = 0; j < N; ++j)
    {
      
      printf("%d	", arr[j]);
    }
    printf("
");
    printf("
");

    }

}

int main(void) {

    int N;
  scanf("%d", &N);
  int arr[N], i;
  for(i = 0; i < N; i++) {
    scanf("%d", &arr[i]);
  }

  printf("Input Array is: ");

  for(i = 0; i < N; i++) {
    printf("%d	", arr[i]);
  }

  printf("

");

    insertionSort(N, arr);
  
  printf("Sortrd Array: 	");

  for(i = 0; i < N; i++) {
    printf("%d	", arr[i]);
  }

  printf("
");

  return 0;
}

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