Insertion Sort in C++

This is a C++ program to sort the given data using Insertion Sort.

Problem Description

1. Insertion sort algorithm sort data by inserting them one by one into the list.
2. The time complexity of this algorithm is O(n^2).

Problem Solution

1. This algorithm is based on sorting playing cards by picking and inserting them one by one.
2. Here we take data element and place it in sorted list.
3. It should be placed so that list remains sorted.
4. Display the result.
5. Exit.

Program/Source Code

C++ program to implement Insertion Sort using linked lists.
This program is successfully run on Dev-C++ using TDM-GCC 4.9.2 MinGW compiler on a Windows system.

#include <iostream>
 
using namespace std;
 
// A structure to represent a node.
struct list
{
	int data;
	list *next;
};
 
// Function implementing insertion sort.
list* InsertinList(list *head, int n)
{
	// Creating newnode and temp node.
	list *newnode = new list;
	list *temp = new list;
 
	// Using newnode as the node to be inserted in the list.
	newnode->data = n;
	newnode->next = NULL;
 
	// If head is null then assign new node to head.
	if(head == NULL)
	{
		head = newnode;
		return head;
	}
	else
	{
		temp = head;
 
		// If newnode->data is lesser than head->data, then insert newnode before head.
		if(newnode->data < head->data)
		{
			newnode->next = head;
			head = newnode;
			return head;
		}
 
		// Traverse the list till we get value more than newnode->data.
		while(temp->next != NULL)
		{
			if(newnode->data < (temp->next)->data)
				break;
 
			temp=temp->next;
		}
 
		// Insert newnode after temp.
		newnode->next = temp->next;
		temp->next = newnode;
		return head;
	}	
}	
 
int main()
{
	int n, i, num;
	// Declaring head of the linked list.
	list *head = new list;
	head = NULL;
 
	cout<<"\nEnter the number of data element to be sorted: ";
	cin>>n;
 
	for(i = 0; i < n; i++)
	{
		cout<<"Enter element "<<i+1<<": ";
		cin>>num;
		// Inserting num in the list.
		head = InsertinList(head, num);
	}
 
	// Display the sorted data.
	cout<<"\nSorted Data ";
	while(head != NULL)
	{
		cout<<"->"<<head->data;
		head = head->next;
	}
 
	return 0;
}

Program Explanation

1. Create a head node of the list structure.
2. Take input of data and simultaneously insert it into a list using InsertinList().
3. Assign the new element as newnode.
4. If the head is null then assign newnode to head.
5. Otherwise, insert the newnode so that list remains sorted.
6. Return head to main.
7. Display the result.
8. Exit.

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Runtime Test Cases

Case 1:(average case)
 
Enter the number of data element to be sorted: 5
Enter element 1: 998
Enter element 2: 451
Enter element 3: 2
Enter element 4: 35
Enter element 5: 1206
 
Sorted Data ->2->35->451->998->1206
 
 
Case 2:(best case)
 
Enter the number of data element to be sorted: 5
Enter element 1: 99845
Enter element 2: 564
Enter element 3: 332
Enter element 4: 86
Enter element 5: 1
 
Sorted Data ->1->86->332->564->99845
 
 
case 3: (worst case)
 
Enter the number of data element to be sorted: 5
Enter element 1: 2
Enter element 2: 332
Enter element 3: 456
Enter element 4: 1024
Enter element 5: 16565
 
Sorted Data ->2->332->456->1024->16565

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