advent-of-code/2023/4/main-1.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int ret = 0;

	string line;
	while (getline(cin, line) && !line.empty()) {
		int count = 1;
		int start = line.find(':');
		int bar = line.find('|');
		string left = line.substr(start + 2, bar - start - 3);
		string right = line.substr(bar + 2);
		istringstream lss(left), rss(right);
		set<int> ls;
		while (!lss.eof()) {
			int n;
			lss >> n;
			ls.insert(n);
		}
		while (!rss.eof()) {
			int n;
			rss >> n;
			if (ls.find(n) != ls.end()) {
				count <<= 1;
			}
		}
		ret += count >> 1;
	}
	cout << ret << '\n';
}