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advent-of-code-2020
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Use reduce in day3

master
Nick Krichevsky 2020-12-03 00:24:50 -05:00
parent 02e256a6cd
commit ed1c1037af
1 changed files with 12 additions and 3 deletions
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15
day3/day3.cpp
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@ -1,5 +1,7 @@
#include <execution>
#include <fstream>
#include <iostream>
#include <numeric>
#include <vector>
constexpr char TREE_CHAR = '#';
@ -39,13 +41,20 @@ int part1(const std::vector<std::string> &input) {
}
long part2(const std::vector<std::string> &input) {
return 1L * findNumTrees(input, 1, 1) * findNumTrees(input, 3, 1) * findNumTrees(input, 5, 1) *
findNumTrees(input, 7, 1) * findNumTrees(input, 1, 2);
// deltas in the x and y directions respectively
std::vector<std::pair<int, int>> deltas{std::pair<int, int>(1, 1), std::pair<int, int>(3, 1),
std::pair<int, int>(5, 1), std::pair<int, int>(7, 1),
std::pair<int, int>(1, 2)};
return std::reduce(std::execution::par, deltas.begin(), deltas.end(), 1L,
[&](long total, std::pair<int, int> step_deltas) {
return total * findNumTrees(input, step_deltas.first, step_deltas.second);
});
}
int main(int argc, char *argv[]) {
if (argc != 2) {
std::cerr << "./" << argv[0] << "<input_file>" << std::endl;
std::cerr << argv[0] << "<input_file>" << std::endl;
return 1;
}