fork download
copy 
  1. #include <iostream>
  2. #include <unordered_map>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7. int countPairsWithDifferenceK(const vector<int>& b, int k) {
  8.     unordered_map<int, int> freq;
  9.     int count = 0;
  10.  
  11.     for (int j = 0; j < b.size(); ++j) {
  12.         if (freq.find(b[j] - k) != freq.end()) {
  13.             count += freq[b[j] - k]; //count++ only works when all elements are unique
  14.         }
  15.         if (k != 0 && freq.find(b[j] + k) != freq.end()) { // to avoid double counting when k = 0
  16.             count += freq[b[j] + k];
  17.         }
  18.  
  19.         freq[b[j]]++;
  20.     }
  21.  
  22.     return count;
  23. }
  24.  
  25. int main() {
  26.     vector<int> b = {1, 5, 3, 4, 2};
  27.     int k = 2;
  28.     cout << countPairsWithDifferenceK(b, k) << endl; // Output should be the number of pairs with difference k
  29.     return 0;
  30. }
  31.  
Success #stdin #stdout 0.01s 5320KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
3
https://ideone.com/VYs4N1
language:
C++ (gcc 8.3)
created:
4 hours ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!