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#include <cctype>
#include <fstream>
#include <iostream>
#include <string>
#include <string_view>
#include <vector>
using namespace std;
vector<string>
read_file(string_view filename)
{
fstream input{ filename };
vector<string> data;
for ( string line; getline(input, line); ) {
data.emplace_back(line);
}
return data;
}
bool
is_digit(char chr)
{
return std::isdigit(static_cast<unsigned char>(chr)) != 0;
}
void
part1() // NOLINT
{
auto lines = read_file("data/day03.txt");
auto is_symbol = [&lines](int row, int col) -> bool {
static const string symbols{ "*#+$%=-@&/" };
if ( row < 0 || col < 0 ) {
return false;
}
if ( size_t(row) >= lines.size() || size_t(col) >= lines[size_t(row)].size() ) {
return false;
}
auto symbol = lines[size_t(row)][size_t(col)];
return symbols.find(symbol) != string::npos;
};
auto bordering = [&is_symbol](int row, int col) -> bool {
bool result = false;
result |= is_symbol(row - 1, col - 1);
result |= is_symbol(row - 0, col - 1);
result |= is_symbol(row + 1, col - 1);
result |= is_symbol(row - 1, col);
result |= is_symbol(row + 1, col);
result |= is_symbol(row - 1, col + 1);
result |= is_symbol(row - 0, col + 1);
result |= is_symbol(row + 1, col + 1);
return result;
};
auto sum = 0;
for ( size_t row = 0; row != lines.size(); ++row ) {
const auto& line = lines[row];
string::size_type start = 0;
while ( start != line.size() ) {
while ( start != line.size() && !is_digit(line[start]) ) {
++start;
}
auto end = start;
while ( end != line.size() && is_digit(line[end]) ) {
++end;
}
if ( start != end ) {
auto result = false;
for ( auto col = start; col != end; ++col ) {
result |= bordering(int(row), int(col));
}
if ( result ) {
sum += stoi(line.substr(start, end - start));
}
start = end;
}
}
}
cout << sum << endl;
}
void
part2()
{
auto lines = read_file("data/day03.txt");
auto find_integer = [](vector<string>& lines, size_t row, size_t col, int& value) -> bool { // NOLINT
if ( row >= lines.size() || col >= lines[row].size() ) {
return false;
}
auto& line = lines[row];
auto digit = line[col];
if ( !is_digit(digit) ) {
return false;
}
// Anfang der Zahl suchen
auto start = col;
for ( ; start != 0 && is_digit(line[start - 1]); --start ) // NOLINT
;
auto end = col;
for ( ; end != line.size() && is_digit(line[end]); ++end ) // NOLINT
;
value = stoi(line.substr(start, end - start));
for ( ; start != end; ++start ) {
line[start] = '.';
}
return true;
};
auto sum = 0;
for ( size_t row = 0; row != lines.size(); ++row ) {
const auto& line = lines[row];
auto col = line.find('*');
while ( col != string::npos ) {
int value = 0;
vector<int> values;
auto lines_copy{ lines };
if ( find_integer(lines_copy, row - 1, col - 1, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row - 0, col - 1, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row + 1, col - 1, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row - 1, col, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row + 1, col, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row - 1, col + 1, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row - 0, col + 1, value) ) {
values.emplace_back(value);
}
if ( find_integer(lines_copy, row + 1, col + 1, value) ) {
values.emplace_back(value);
}
if ( values.size() == 2 ) {
auto ratio = values[0] * values[1];
sum += ratio;
}
col = line.find('*', col + 1);
}
}
cout << sum << endl;
}
int
main()
{
part2();
}
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