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#include "aoc.h"
#include <stack>
namespace aoc2017 {
static void take(const char* p, std::stack<char>& gs, int* t) {
if (*p == '{') {
gs.push(*p);
}
if (*p == '}') {
*t += gs.size();
gs.pop();
}
}
static bool is_valid(const char* p, std::stack<char>& g) {
if (g.empty()) {
if (*p == '!') {
g.push(*p);
}
if (*p == '<') {
g.push(*p);
}
} else {
if (g.top() == '!') {
g.pop();
} else {
if (*p == '>') {
g.pop();
}
if (*p == '!') {
g.push(*p);
}
}
}
return g.empty();
}
int day9(line_view file) {
int t0{0};
std::stack<char> gs;
std::stack<char> gv;
const char* p = file.line;
while (p < file.line + file.length) {
if (is_valid(p, gv)) {
take(p, gs, &t0);
}
p++;
}
return t0;
}
} // namespace aoc2017
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