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Implement n log n advancement.

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Bert Peters
2019-12-16 13:10:51 +01:00
parent c46f0f9e2e
commit 596e8ccde3
1 changed files with 7 additions and 17 deletions
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24
2019/src/day16.cpp
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@@ -41,9 +41,13 @@ namespace {
new_numbers.reserve(numbers.size()); new_numbers.reserve(numbers.size());
for (int rank = 0; rank < numbers.size(); ++rank) { for (int rank = 0; rank < numbers.size(); ++rank) {
auto partial_sums = partial_sum(numbers);
int n = 0; int n = 0;
for (int pos = rank; pos < numbers.size(); ++pos) { for (int pos = rank; pos < numbers.size(); pos += rank + 1) {
n += get_modifier(rank, pos) * numbers[pos]; int run = std::min(rank + 1, (int) numbers.size() - pos);
if (int modifier = get_modifier(rank, pos); modifier) {
n += modifier * (partial_sums[pos + run - 1] - partial_sums[pos] + numbers[pos]);
}
} }
n = std::abs(n % 10); n = std::abs(n % 10);
@@ -59,21 +63,7 @@ void aoc2019::day16_part1(std::istream &input, std::ostream &output) {
auto numbers = read_input(input); auto numbers = read_input(input);
for (int i = 0; i < 100; ++i) { for (int i = 0; i < 100; ++i) {
std::vector<int> new_numbers; numbers = advance(numbers);
new_numbers.reserve(numbers.size());
for (int rank = 0; rank < numbers.size(); ++rank) {
int n = 0;
for (int pos = rank; pos < numbers.size(); ++pos) {
n += get_modifier(rank, pos) * numbers[pos];
}
n = std::abs(n % 10);
new_numbers.push_back(n);
}
numbers = new_numbers;
} }
std::copy(numbers.begin(), numbers.begin() + 8, std::ostream_iterator<int>(output)); std::copy(numbers.begin(), numbers.begin() + 8, std::ostream_iterator<int>(output));