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advent-of-code-2020
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Add solution for day 9 part 2

master
Nick Krichevsky 2020-12-09 00:43:28 -05:00
parent 1948ffb648
commit ddc1947f59
1 changed files with 19 additions and 1 deletions
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20
day9/day9.cpp
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@ -56,7 +56,7 @@ bool numberThatSumsInRange(int total, int candidate, Iter start, Iter end) {
return false;
}
int part1(const std::vector<long> &numbers) {
long part1(const std::vector<long> &numbers) {
for (auto checkIterator = numbers.begin() + PREAMBLE_SIZE; checkIterator != numbers.end(); checkIterator++) {
auto rangeStart = checkIterator - PREAMBLE_SIZE;
auto rangeEnd = checkIterator;
@ -76,6 +76,23 @@ int part1(const std::vector<long> &numbers) {
throw std::invalid_argument("No solution in input");
}
long part2(const std::vector<long> &numbers) {
long desired = part1(numbers);
for (auto rangeStartIterator = numbers.begin(); rangeStartIterator != numbers.end(); rangeStartIterator++) {
for (auto rangeEndIterator = rangeStartIterator + 1; rangeEndIterator != numbers.end(); rangeEndIterator++) {
auto total = std::accumulate(
rangeStartIterator, rangeEndIterator, 0, [](int num, int total) { return num + total; });
if (total == desired) {
auto min = std::min_element(rangeStartIterator, rangeEndIterator);
auto max = std::max_element(rangeStartIterator, rangeEndIterator);
return *min + *max;
}
}
}
throw std::invalid_argument("No solution in input");
}
int main(int argc, char *argv[]) {
if (argc != 2) {
std::cerr << argv[0] << " <input_file>" << std::endl;
@ -86,4 +103,5 @@ int main(int argc, char *argv[]) {
auto numbers = convertInputToNumbers(input);
std::cout << part1(numbers) << std::endl;
std::cout << part2(numbers) << std::endl;
}