Find K Closest Elements in C++

Suppose we have a sorted array, two integers k and x are also given, we have to find the k closest elements to x in that array. The result should be sorted in increasing order. If there is a tie, the smaller elements are always preferred. So if the input is like [1,2,3,4,5] and k = 4, x = 3, then output will be [1,2,3,4]

To solve this, we will follow these steps −

• Make an array called ans
• set low := 0, high := size of the array – k
• while low < high
  • mid := low + (high - low) /2
  • if x – arr[mid] > arr[mid + k] – x, then low := mid + 1, otherwise high := mid
• for i in range low to low + k
  • insert arr[i] into ans array
• return ans

Example(C++)

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h> using namespace std; void print_vector(vector<auto> v){    cout << "[";    for(int i = 0; i<v.size(); i++){       cout << v[i] << ", ";    } cout << "]"<<endl; } class Solution { public:    vector<int> findClosestElements(vector<int>& arr, int k, int x) {       vector <int> ans;       int low = 0;       int high = arr.size() - k;       while(low < high){          int mid = low + (high - low)/2;          if(x - arr[mid] > arr[mid + k] - x){             low = mid + 1;          }          else high = mid;       }       for(int i = low ; i < low + k ; i++)ans.push_back(arr[i]);       return ans;    } }; main(){    Solution ob;    vector<int> v = {1,2,3,4,5};    print_vector(ob.findClosestElements(v, 4, 3)); }

Input

[1,2,3,4,5] 4 3

Output

[1,2,3,4]