How to find the Kth smallest number given in the array using C++

Question:

How to find the Kth smallest number given in the array using C++

Summary

The method we'll use keeps track of the first k elements in the array's priority queue. For each new element, it compares it to the highest element in the priority queue.

You can use various algorithms to find the Kth smallest number in an array. This includes accessing the Kth element and sorting the array or by using algorithms like heaps or quickstyles. The following is the simple implementation using the stranded library function ‘std::nth_element()’ in C++.

#include <iostream>

#include <vector>

#include <algorithm>

int findKthSmallest(std::vector<int>& nums, int k) {

// Check if k is within the bounds of the array

if (k < 1 || k > nums.size()) {

std::cerr << "Invalid value of k\n";

return -1; // Return a sentinel value indicating failure

}

// Use std::nth_element to partially sort the array

std::nth_element(nums.begin(), nums.begin() + k - 1, nums.end());

// The kth smallest element is now at index k-1

return nums[k - 1];

}

int main() {

std::vector<int> nums = {7, 10, 4, 3, 20, 15};

int k = 3; // Find the 3rd smallest element

int kth_smallest = findKthSmallest(nums, k);

if (kth_smallest != -1) {

std::cout << "The " << k << "th smallest element is: " << kth_smallest << std::endl;

} else {

std::cerr << "Failed to find the kth smallest element\n";

}

return 0;

}

In the above code, the function ‘findKthSmallest’ takes the value of K as input takes a vector of integers, and returns the Kth smallest element in the array. To partially sort the array to the Kth position it uses ‘std::nth_element()’. After this, it returns the element at index ‘k-1’.

For the code to work, you must include iostream>, vector>, and algorithm> headers. Ensure that edge cases, e.g. when k is out of bounds or if an array has no value, are handled properly.

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