Competitive_Programming/subsetSum.cpp at main · ikshitd/Competitive_Programming · GitHub

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#include <bits/stdc++.h>

using namespace std;

#define int            long long int
#define F              first
#define S              second
#define pb             push_back
#define si             set <int>
#define vi             vector <int>
#define pii            pair <int, int>
#define vpi            vector <pii>
#define vpp            vector <pair<int, pii>>
#define mii            map <int, int>
#define mpi            map <pii, int>
#define spi            set <pii>
#define endl           "\n"
#define sz(x)          ((int) x.size())
#define all(p)         p.begin(), p.end()
#define double         long double
#define que_max        priority_queue <int>
#define que_min        priority_queue <int, vi, greater<int>>
#define bug(...)       __f (#__VA_ARGS__, __VA_ARGS__)
#define print(a)       for(auto x : a) cout << x << " "; cout << endl
#define print1(a)      for(auto x : a) cout << x.F << " " << x.S << endl
#define print2(a,x,y)  for(int i = x; i < y; i++) cout<< a[i]<< " "; cout << endl
#define read(a , n)	   for(int i = 0 ;i < n; i++) cin >> arr[i] ;

inline int power(int a, int b)
{
	int x = 1;
	while (b)
	{
		if (b & 1) x *= a;
		a *= a;
		b >>= 1;
	}
	return x;
}

template <typename Arg1>
void __f (const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << endl; }
template <typename Arg1, typename... Args>
void __f (const char* names, Arg1&& arg1, Args&&... args)
{
	const char* comma = strchr (names + 1, ',');
	cout.write (names, comma - names) << " : " << arg1 << " | "; __f (comma + 1, args...);
}

const int N = 200005;

vector <int> subsetsum(vector <int> a){

	vector <int> res ;

	int n = a.size() ;
	for(int i = 0 ;i < (1 << n) ; i++){
		int sum = 0 ;
		for(int j = 0;j < n ; j++){
			if((i >> j) & 1 == 1){
				sum += a[j] ;
			}
		}
		res.pb(sum) ;
	}
	return res ;
}
void solve() {
	int n  , a , b ;
	cin >> n >> a >> b ;
	int arr[n] ;
	read(arr , n );
	vector <int> left ;
	vector <int> right ;
	for(int i = 0 ;i < n ; i++){
		if(i <= (n/ 2)){
			left.pb(arr[i]);
		}
		else{
			right.pb(arr[i]);
		}
	}
	vector <int> left_sums = subsetsum(left) ;
	vector <int> right_sums = subsetsum(right) ;
	sort(right_sums.begin() , right_sums.end()) ;

	int ans = 0 ;
	for(auto x : left_sums){
		ans += (upper_bound(right_sums.begin() , right_sums.end() , b - x) - lower_bound(right_sums.begin() , right_sums.end() , a - x));
	}
	cout << ans << endl ;
	return ;
}

int32_t main()
{
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

#ifndef ONLINE_JUDGE
	freopen("input.txt",  "r",  stdin);
	freopen("output.txt", "w", stdout);
#endif

	clock_t z = clock();

	int t = 1;
	// cin >> t;
	while (t--) solve();

	cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC);

	return 0;
}