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#pragma once
#include "common.h"
#include <algorithm>
namespace aoc2021 {
struct heightmap {
// 0 .. 99
static const int grid = 100;
static int areas[grid * grid];
struct hchar {
char value = 0;
char checked = 0;
};
hchar hs[grid * grid];
void load(int r, line_view lv) {
const char* p = lv.line;
for(int i = 0; i < grid; i++) {
hs[grid * r + i].value = *(p + i) - '0';
}
}
void low_point(int x, int y, int* d) const noexcept {
char l = x == 0 ? 10 : hs[grid * y + x - 1].value;
char r = x == grid - 1 ? 10 : hs[grid * y + x + 1].value;
char t = y == 0 ? 10 : hs[grid * (y - 1) + x].value;
char b = y == grid - 1 ? 10 : hs[grid * (y + 1) + x].value;
char n = hs[grid * y + x].value;
if (n < l && n < r && n < t && n < b) {
*d += n + 1;
}
}
void basin(int x, int y, int* area) {
if (hs[grid * y + x].value < 9 && hs[grid * y + x].checked == 0) {
*area += 1;
hs[grid * y + x].checked = 1;
std::pair<char, char> ps[4] = {{x-1, y}, {x+1, y}, {x, y-1}, {x, y+1}};
for (auto& p : ps) {
if (p.first >= 0 && p.first < grid && p.second >= 0 && p.second < grid) {
basin(p.first, p.second, area);
}
}
}
}
int risks() const noexcept {
int r{0};
for (int y = 0; y < grid; y++) {
for (int x = 0; x < grid; x++) {
low_point(x, y, &r);
}
}
return r;
}
int top3() {
for (int y = 0; y < grid; y++) {
for (int x = 0; x < grid; x++) {
areas[y * grid + x] = 0;
basin(x, y, &areas[y * grid + x]);
}
}
std::sort(areas, areas + grid * grid, [](int x, int y){ return x > y;});
return areas[0] * areas[1] * areas[2];
}
};
std::pair<int, int> day9(line_view file);
}
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