Submission #855334

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
long long N, A;
int x[50];
int main() {
	cin >> N >> A;
	for (int i = 0; i < N; ++ i) cin >> x[i];
	map<pair<int, int>, long long> cnt1, cnt2;
	for (int i = 0; i < 1<<(N/2); ++ i) {
		int sum = 0, c = 0;
		for (int j = 0; j < N/2; ++ j) if ((i>>j)&1) { sum += x[j]; ++ c; }
		++ cnt1[{sum, c}];
	}
	for (int i = 0; i < 1<<(N-N/2); ++ i) {
		int sum = 0, c = 0;
		for (int j = 0; j < N-N/2; ++ j) if ((i>>j)&1) { sum += x[j+N/2]; ++ c; }
		++ cnt2[{sum, c}];
	}
	long long r = 0;
	for (auto p : cnt1) {
		for (int i = 0; i <= N-N/2; ++ i) {
			int c = p.first.second + i;
			int x = A * c - p.first.first;
			if (c == 0) continue;
			if (cnt2.count({x, i})) r += p.second * cnt2[{x, i}];
		}
	}
	cout << r << endl;
}

Submission Info

Judge Result