Kth Largest Element In An Array

When working with arrays, it’s often necessary to find the Kth largest element, where K is a positive integer. While there are efficient algorithms like the QuickSelect algorithm for this task, let’s start by understanding the brute force method – a straightforward approach to solving this problem. In this blog, we’ll walk you through the process step by step and provide you with a code snippet to help you grasp the concept.

Algorithm Overview

The brute force method to find the Kth largest element involves iterating through the array, comparing each element with the rest, and keeping track of the Kth largest element encountered so far. Let’s break down the approach:

1. Initialize a variable to keep track of the Kth largest element.
2. Loop through the array.
3. For each element, compare it with the current Kth largest element.
4. If the element is greater than the current Kth largest element, update the Kth largest element.
5. Continue this process until you have iterated through the entire array.
6. The final value of the Kth largest element will be the desired result.

Implementation in C++

#include <iostream>
#include <vector>

using namespace std;

int findKthLargest(vector<int>& nums, int k) {
    // Ensure that k is a valid index within the array
    if (k < 1 || k > nums.size()) {
        cout << "Invalid value of k. Exiting..." << endl;
        exit(EXIT_FAILURE);
    }

    // Basic selection sort to find the kth largest element
    for (int i = 0; i < k; ++i) {
        int max_idx = i;
        for (int j = i + 1; j < nums.size(); ++j) {
            if (nums[j] > nums[max_idx]) {
                max_idx = j;
            }
        }
        // Swap the elements
        int temp = nums[i];
        nums[i] = nums[max_idx];
        nums[max_idx] = temp;
    }

    return nums[k - 1];
}

int main() {
    vector<int> arr = {3, 1, 7, 5, 8, 2, 4, 6};
    int k = 4;

    int kth_largest = findKthLargest(arr, k);
    cout << "The " << k << "th largest element is: " << kth_largest << endl;

    return 0;
}

Conclusion

While the brute force method is straightforward and easy to understand, it may not be the most efficient solution for large arrays. In such cases, algorithms like QuickSelect offer better time complexity. However, understanding the brute force method lays the foundation for grasping more complex algorithms. We hope this blog has provided you with a clear understanding of how to find the Kth largest element using brute force. Feel free to explore more advanced algorithms for optimizing this task further.