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#include <numeric>
#include <cassert>
#include <print>
#include <iostream>
#include <vector>
#include <ranges>
#include <algorithm>
#include <sstream>
namespace ranges = std::ranges;
namespace views = std::views;
const auto parse_input() {
std::vector<std::vector<int>> result;
for (std::string s; std::getline(std::cin, s);) {
std::stringstream ss{s};
std::vector<int> row;
for (int l; ss >> l;) {
row.push_back(l);
}
result.push_back(row);
}
return result;
}
bool safe_report(const auto &report) {
assert(report.size() > 0);
std::vector<int> _diffs(report.size());
std::adjacent_difference(report.begin(), report.end(), _diffs.begin());
// The first diff is from 0 (zero) to the first layer, so we ignore it
const auto diffs = ranges::subrange(_diffs.begin() + 1, _diffs.end());
const bool ascending = std::count_if(diffs.begin(), diffs.end(), [](int d) {
return d > 0;
}) > (diffs.size() / 2);
const bool safe = ranges::all_of(diffs, [ascending](int d) {
const bool bounded = (1 <= std::abs(d) and std::abs(d) <= 3);
const bool monotonic = ((d > 0 and ascending) or (d < 0 and not ascending));
return monotonic and bounded;
});
return safe;
}
void part1(const auto &input) {
int answer{0};
for (const auto &report : input) {
if (safe_report(report)) {
++answer;
}
}
std::println("{}", answer);
}
void part2(const auto &input) {
int answer{0};
for (const auto &report : input) {
if (ranges::any_of(views::iota(size_t(0), report.size()), [&report](size_t i) {
return safe_report(views::concat(report | views::take(i),
report | views::drop(i + 1)));
})) {
++answer;
}
}
std::println("{}", answer);
}
int main() {
const auto input = parse_input();
#ifndef NO_PART1
part1(input);
#endif
#ifndef NO_PART2
part2(input);
#endif
return 0;
}
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