C++ Program to Find the Mode of a Data Set

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This is a C++ program to find the Mode in a Dataset.

Problem Description

1. The mode is the maximum of the count of occurrence of the different data element.
2. This algorithm is beneficial for a large dataset with high repetition frequency.
3. The worst case time complexity of this algorithm is O(n^2).

Problem Solution

1. This algorithm inserts the distinct data into linked list in a sorted manner.
2. Instead of inserting same data twice it records the occurrence of each data element.
3. The maximum occurred among these is the Mode.
4. Exit.

Program/Source Code

C++ Program to Find the Mode in a Data Set.
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;
	int count;
	list *next;
};
 
// Function to insert data into linked list.
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->count = 0;
	newnode->next = NULL;
 
	// If head is null then assign new node to head and increase the count.
	if(head == NULL)
	{
		head = newnode;
		head->count++;
		return head;
	}
	else
	{
		temp = head;
 
		// If newnode->data is lesser than head->data, then insert newnode before head and increase the count.
		if(newnode->data < head->data)
		{
			newnode->next = head;
			head = newnode;
			newnode->count++;
			return head;
		}
		// If newnode->data is equal to the head data then increase count of the head node.
		else if(newnode->data == head->data)
		{
			head->count++;
			return head;
		}
 
		// Traverse the list till we get value more than or equal to the newnode->data.
		while(temp->next != NULL)
		{
			// If equals to any of the data present in the list then increse the counter and return.
			if(newnode->data == (temp->next)->data)
			{
				(temp->next)->count++;
				return head;
			}
			if(newnode->data < (temp->next)->data)
				break;
 
			temp=temp->next;
		}
 
		// Insert newnode after temp.
		newnode->next = temp->next;
		temp->next = newnode;
		// Increase the counter.
		newnode->count++;
		return head;
	}	
}	
 
int main()
{
    int n, i, num, max = 0, c;
    // 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);
	}
 
	// Printing the sorted data.
	cout<<"\nSorted Distinct Data ";
 
	while(head != NULL)
	{
    		if(max < head->count)
    		{
    			c = head->data;
			max = head->count;
		}
		cout<<"->"<<head->data<<"("<<head->count<<")";
		head = head->next;
	}
 
	cout<<"\nThe Mode of given data is "<<c<<" and occurred "<<max<<" times.";
	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. During insertion, sort the data using the concept of insertion sort.
4. If the newnode->data is equal to any of the element present in the list then just increment count.
5. Return to main and find the maximum of the count data member of each node.
6. print the maximum occurred data and its count.
7. Exit.

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Runtime Test Cases
Case 1:
Enter the number of data element to be sorted: 20
Enter element 1: 2
Enter element 2: 6
Enter element 3: 5
Enter element 4: 9
Enter element 5: 8
Enter element 6: 4
Enter element 7: 2
Enter element 8: 3
Enter element 9: 1
Enter element 10: 2
Enter element 11: 0
Enter element 12: 1
Enter element 13: 0
Enter element 14: 2
Enter element 15: 8
Enter element 16: 5
Enter element 17: 4
Enter element 18: 2
Enter element 19: 6
Enter element 20: 2
 
Sorted Distinct Data ->0(2)->1(2)->2(6)->3(1)->4(2)->5(2)->6(2)->8(2)->9(1)
The Mode of given data is 2 and occurred 6 times.

Sanfoundry Global Education & Learning Series – C++ Algorithms.
To practice all C++ Algorithms, here is complete set of 1000 C++ Algorithms.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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