C++ Find Top K most Frequent elements in sorted Vector using Pair Template

Hello Everyone!

In this tutorial, we will learn about Finding the top k most frequent elements in a sorted Vector, in the C++ programming language.

To understand the basic functionality of the Pair Template, we will recommend you visit, C++ STL Pair Template, where we have explained this concept in detail from scratch.

For a better understanding of its implementation, refer to the well-commented C++ code given below.

Code:

 #include <iostream> #include <bits/stdc++.h> using namespace std; vector<int> topKFrequent(vector<int> &a, int k) { unordered_map<int, int> u; int n = a.size(); int i; for (i = 0; i < n; i++) { u[a[i]]++; } vector<pair<int, int>> v(u.begin(), u.end()); sort(v.begin(), v.end(), [](pair<int, int> x, pair<int, int> y) { if (x.second == y.second) return x.first < y.first; else return x.second > y.second; }); vector<int> r; for (i = 0; i < k; i++) { r.push_back(v[i].first); } return r; } int main() { cout << "\n\nWelcome to Studytonight :-)\n\n\n"; cout << " ===== Program to find the top k most frequent elements in a vector, in CPP ===== \n\n\n"; //initializing vector with the following elements vector<int> v = {1, 2, 3, 1, 2, 1}; vector<int> f; int k = 2; //to find the 2 most frequent numbers int n = v.size(); cout << "The elements of the given vector is : "; for (int i = 0; i < n; i++) { cout << v[i] << " "; } f = topKFrequent(v, k); n = f.size(); cout << "\n\n The top " << k << " most frequent numbers are: "; for (int i = 0; i < n; i++) { cout << f[i] << " "; } cout << "\n\n\n"; return 0; }

Output:

We hope that this post helped you develop a better understanding of the concept of the application of a Pair Template and its implementation in C++. For any query, feel free to reach out to us via the comments section down below.

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