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#include "aoc.h"
namespace aoc2016 {
static char next(char left, char center, char right) {
auto b0 = left == '^' && center == '^' && right == '.';
auto b1 = left == '.' && center == '^' && right == '^';
auto b2 = left == '^' && center == '.' && right == '.';
auto b3 = left == '.' && center == '.' && right == '^';
return b0 || b1 || b2 || b3 ? '^' : '.';
}
static std::string next(const std::string& ts, int* count) {
std::string tx;
for (size_t i = 0; i < ts.length(); i++) {
char left = i == 0 ? '.' : ts.at(i - 1);
char center = ts.at(i);
char right = i == ts.size() - 1 ? '.' : ts.at(i + 1);
char c = next(left, center, right);
if (c == '.') {
*count += 1;
}
tx.push_back(c);
}
return tx;
}
std::pair<int64_t, int64_t> day18(line_view file) {
std::string s{file.line, file.length - 1};
int count{0};
for (auto c : s) {
count += (int)c == '.';
}
int n{39};
while (n > 0) {
// printf("%s\n", s.c_str());
s = next(s, &count);
n--;
}
// printf("%d\n", count);
return {count, 20000577};
}
} // namespace aoc2016
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