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Number of subsets with product less than k .cpp
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/*
Question Link--
https://practice.geeksforgeeks.org/problems/number-of-subsets-with-product-less-than-k/1#
Solved by https://www.linkedin.com/in/whynesspower
Pre-requisite - Meet in the middle approch for CP
*/
// { Driver Code Starts
#include <bits/stdc++.h>
using namespace std;
// } Driver Code Ends
//User function Template for C++
class Solution
{
public:
int numOfSubsets(int arr[], int n, int k)
{
// declare four vector for dividing array into
// two halves and storing product value of
// possible subsets for them
vector<int> vect1, vect2, subset1, subset2;
// ignore element greater than k and divide
// array into 2 halves
for (int i = 0; i < n; i++)
{
// ignore element if greater than k
if (arr[i] > k)
continue;
if (i <= n / 2)
vect1.push_back(arr[i]);
else
vect2.push_back(arr[i]);
}
// generate all subsets for 1st half (vect1)
for (int i = 0; i < (1 << vect1.size()); i++)
{
int value = 1;
for (int j = 0; j < vect1.size(); j++)
{
if (i & (1 << j))
value *= vect1[j];
if (value > k)
break;
}
// push only in case subset product is less
// than equal to k
if (value <= k)
subset1.push_back(value);
}
// generate all subsets for 2nd half (vect2)
for (int i = 0; i < (1 << vect2.size()); i++)
{
int value = 1;
for (int j = 0; j < vect2.size(); j++)
{
if (i & (1 << j))
value *= vect2[j];
if (value > k)
break;
}
// push only in case subset product is
// less than equal to k
if (value <= k)
subset2.push_back(value);
}
// sort subset2
sort(subset2.begin(), subset2.end());
int count = 0;
for (int i = 0; i < subset1.size(); i++)
count += upper_bound(subset2.begin(), subset2.end(),
(k / subset1[i])) -
subset2.begin();
// for null subset decrement the value of count
count--;
// return count
return count;
}
};
// { Driver Code Starts.
int main()
{
int t;
cin >> t;
while (t--)
{
int N, K;
cin >> N;
int arr[N];
for (int i = 0; i < N; i++)
cin >> arr[i];
cin >> K;
Solution ob;
cout << ob.numOfSubsets(arr, N, K) << endl;
}
return 0;
} // } Driver Code Ends