HackerEarth Chocolates and Boxes problem solution YASH PAL, 31 July 202413 February 2026 In this HackerEarth Chocolates and Boxes, problem-solution Alice has N boxes, and each box has a certain non-zero number of chocolates. These boxes are numbered from 1 to N. Alice is planning to go to wonderland. She wants to carry exactly K number of chocolates and she can carry only 2 boxes. So she wants to know the number of ways in which she can select 2 boxes such that the total number of chocolates in them is K. HackerEarth Chocolates and Boxes problem solution.int main(){ int t; cin>>t; while(t--) { int n; cin>>n; int arr[300000]; rep(i,n) cin>>arr[i]; int k; cin>>k; int mul[300000]; for(int i=0;i<k;i++) mul[i]=0; long long int ways=0; for(int i=0;i<n;i++) { if(arr[i]<k) mul[arr[i]%k]++; } for(int i=1;i<=(k/2);i++) { if(2*i == k && mul[i]>=2) ways+=(mul[i]*(mul[i]-1)/2); else ways+=mul[i]*mul[k-i]; } cout<<ways<<endl; } return 0;} coding problems solutions HackerEarth HackerEarth