Majority Element Moore's Voting Algorithm in DSA C - Build from Scratch

Majority Element Moore's Voting Algorithm

📖 Scenario: Imagine you have a list of votes for candidates in a small election. You want to find out if there is a candidate who got more than half of the votes. This is called the majority element.

🎯 Goal: You will write a program in C to find the majority element in an array of integers using Moore's Voting Algorithm. If a majority element exists, print it; otherwise, print -1.

📋 What You'll Learn

Create an integer array called votes with the exact values: {2, 2, 1, 1, 1, 2, 2}

Create an integer variable called size and set it to the length of the votes array

Implement Moore's Voting Algorithm to find the candidate for majority element using variables candidate and count

Verify if the candidate is actually the majority element by counting its occurrences

Print the majority element if it exists, otherwise print -1

💡 Why This Matters

🌍 Real World

Finding a majority element is useful in elections, surveys, and data analysis where you want to identify the most common choice or value.

💼 Career

Understanding Moore's Voting Algorithm helps in roles involving data processing, algorithm design, and software development where efficient majority detection is needed.

1

Create the votes array

Create an integer array called votes with the exact values {2, 2, 1, 1, 1, 2, 2}.

DSA C

# Your code here

Hint

Use int votes[] = {2, 2, 1, 1, 1, 2, 2}; to create the array.

2

Set the size variable

Create an integer variable called size and set it to the length of the votes array using sizeof(votes) / sizeof(votes[0]).

DSA C

int votes[] = {2, 2, 1, 1, 1, 2, 2};
# Your code here

Hint

Use int size = sizeof(votes) / sizeof(votes[0]); to get the array length.

3

Find the candidate using Moore's Voting Algorithm

Implement Moore's Voting Algorithm to find the candidate for majority element. Use integer variables candidate and count. Initialize candidate to votes[0] and count to 1. Then use a for loop from i = 1 to i < size to update candidate and count as per the algorithm.

DSA C

int votes[] = {2, 2, 1, 1, 1, 2, 2};
int size = sizeof(votes) / sizeof(votes[0]);
// Your code here

Hint

Use a loop to update candidate and count as you compare each vote.

4

Verify and print the majority element

Count how many times candidate appears in votes. If it appears more than size / 2, print candidate. Otherwise, print -1. Use a for loop with variable i to count occurrences, then use printf to print the result.

DSA C

int votes[] = {2, 2, 1, 1, 1, 2, 2};
int size = sizeof(votes) / sizeof(votes[0]);

int candidate = votes[0];
int count = 1;
for (int i = 1; i < size; i++) {
    if (votes[i] == candidate) {
        count++;
    } else {
        count--;
        if (count == 0) {
            candidate = votes[i];
            count = 1;
        }
    }
}
// Your code here

Hint

Count how many times candidate appears and print it if it is majority; else print -1.