Today we will read on this article – Random pick with weight in C ++: If we have an array of positive integers, w [i] describes the weight of the index, we have to define a function pickIndex (), Which randomly chooses an index in proportion to its weight.

Example

#include <bits/stdc++.h>
using namespace std;
class program{
   public:
   int n;
   vector <int> v;
   Solution(vector<int>& w) {
      srand(time(NULL));
      n = w[0];
      for(int i = 1; i < w.size(); i++){
         w[i] += w[i - 1];
         n = w[i];
      }
      v = w;
   }
   int pickIndex() {
      return upper_bound(v.begin(), v.end(), rand() % v.back()) - v.begin();
   }
};
main(){
   vector<int> v = {1,3};
   Solution ob(v);
   cout << (ob.pickIndex()) << endl;
   cout << (ob.pickIndex()) << endl;
   cout << (ob.pickIndex()) << endl;
   cout << (ob.pickIndex()) << endl;
   cout << (ob.pickIndex()) << endl;
}

Input

Initialize with [1, 3] and call pickIndex five times.

Output

1
1
1
1
0