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#include "aoc.h"
namespace aoc2017 {
enum class direction {
up,
right,
down,
left,
};
struct heading {
pos p;
direction d;
};
static heading next(heading h) {
switch (h.d) {
case direction::up:
return {{h.p.x, h.p.y - 1}, h.d};
case direction::right:
return {{h.p.x + 1, h.p.y}, h.d};
case direction::down:
return {{h.p.x, h.p.y + 1}, h.d};
case direction::left:
return {{h.p.x - 1, h.p.y}, h.d};
}
return h;
}
// + or A-Z
static heading next(heading h, alpha_grid& g) {
char c = g.get(h.p);
if (c == '+' || (c >= 'A' && c <= 'Z')) {
heading l = {{h.p.x - 1, h.p.y}, direction::left};
heading r = {{h.p.x + 1, h.p.y}, direction::right};
heading u = {{h.p.x, h.p.y - 1}, direction::up};
heading d = {{h.p.x, h.p.y + 1}, direction::down};
heading hs[4][3] = {{l, r, u}, {u, d, r}, {l, r, d}, {u, d, l}};
for (auto hx : hs[(int)h.d]) {
if (g.get(hx.p) != ' ') {
return hx;
}
}
}
return next(h);
}
static void move(heading h, alpha_grid& g, std::string& alpha) {
while (true) {
char c = g.get(h.p);
if (c == ' ')
break;
if (c >= 'A' && c <= 'Z') {
alpha.push_back(c);
}
h = next(h, g);
}
}
std::pair<std::string, int64_t> day19(line_view file) {
alpha_grid g{200, 200}; // input
// alpha_grid g{15, 6}; // demo
int r{0};
per_line(file, [&g, &r](line_view lv) {
g.load(r++, lv);
return true;
});
heading start = {g.start, direction::down};
std::string alpha{""};
move(start, g, alpha);
return {alpha, 0};
}
} // namespace aoc2017
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