Insertion sort is a simple sorting algorithm that works the way we sort playing cards in our hands.
Insertion Sort
Algorithm
// Sort an arr[] of size n
insertionSort(arr, n)
Loop from i = 1 to n-1.
……a) Pick element arr[i] and insert it into sorted sequence arr[0…i-1]
Example:
12, 11, 13, 5, 6
Let us loop for i = 1 (second element of the array) to 5 (Size of input array)
i = 1. Since 11 is smaller than 12, move 12 and insert 11 before 12
11, 12, 13, 5, 6
i = 2. 13 will remain at its position as all elements in A[0..I-1] are smaller than 13
11, 12, 13, 5, 6
i = 3. 5 will move to the beginning and all other elements from 11 to 13 will move one position ahead of their current position.
5, 11, 12, 13, 6
i = 4. 6 will move to position after 5, and elements from 11 to 13 will move one position ahead of their current position.
5, 6, 11, 12, 13
Code:
Insertion Sort
Algorithm
// Sort an arr[] of size n
insertionSort(arr, n)
Loop from i = 1 to n-1.
……a) Pick element arr[i] and insert it into sorted sequence arr[0…i-1]
Example:
12, 11, 13, 5, 6
Let us loop for i = 1 (second element of the array) to 5 (Size of input array)
i = 1. Since 11 is smaller than 12, move 12 and insert 11 before 12
11, 12, 13, 5, 6
i = 2. 13 will remain at its position as all elements in A[0..I-1] are smaller than 13
11, 12, 13, 5, 6
i = 3. 5 will move to the beginning and all other elements from 11 to 13 will move one position ahead of their current position.
5, 11, 12, 13, 6
i = 4. 6 will move to position after 5, and elements from 11 to 13 will move one position ahead of their current position.
5, 6, 11, 12, 13
Code:
// C program for insertion sort
#include<iostream>
#include<math.h>
using namespace std;
/* 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 ot print an array
of size n
void printArray(int arr[], int n)
{
int i;
for (i = 0; i < n; i++)
cout
<< arr[i] << endl;
}
/* 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;
}
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