K’th Smallest/Largest Element using STL in C++

In this tutorial, we are going to write a program that finds the k-th smallest number in the unsorted array.

Let's see the steps to solve the problem.

• Initialise the array and k.
• Initialise a empty ordered set.
• Iterate over the array and insert each element to the array.
• Iterate over the set from 0 to k - 1.
• Return the value.

Example

Let's see the code.

 Live Demo

#include <bits/stdc++.h>
using namespace std;
int findKthSmallestNumber(int arr[], int n, int k) {
   set<int> set;
   for (int i = 0; i < n; i++) {
      set.insert(arr[i]);
   }
   auto it = set.begin();
   for (int i = 0; i < k - 1; i++) {
      it++;
   }
   return *it;
}
int main() {
   int arr[] = { 45, 32, 22, 23, 12 }, n = 5, k = 3;
   cout << findKthSmallestNumber(arr, n, k) << endl;
   return 0;
}

Output

If you run the above code, then you will get the following result.

23

Conclusion

If you have any queries in the tutorial, mention them in the comment section.