Advent of Code 2020 - Day 6 Custom Customs

day06_custom_customs.cpp

#include <iostream>
#include <string>
#include <set>
using namespace std;

#define endl "\n"

int main() {
    string line;
    int part1_answer=0, part2_answer=0;
    int group_OR=0, group_AND, person_OR;
    group_AND = ~group_OR;      // AND reset, set all bits

    while (getline(cin, line)) {
        if (line == "") {       // next group
            part1_answer += __builtin_popcount(group_OR);
            part2_answer += __builtin_popcount(group_AND);
            group_OR = 0;
            group_AND = ~group_OR;
        } else {
            person_OR = 0;
            for(char &c : line) {
                person_OR |= 1 << (c-96);
                group_OR |= person_OR;
            }
            group_AND &= person_OR;
        }
    }
    part1_answer += __builtin_popcount(group_OR);
    part2_answer += __builtin_popcount(group_AND);

    cout << "Part 1: " << part1_answer << endl;
    cout << "Part 2: " << part2_answer << endl;

    return 0;
}