blog/static/files/algorithms/paths/bf-to-astar/graph.hpp
2024-01-03 15:08:54 +01:00

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#ifndef _GRAPH_HPP
#define _GRAPH_HPP
#include <cmath>
#include <limits>
#include <ostream>
#include <utility>
#include <vector>
using vertex_t = std::pair<int, int>;
struct graph {
graph(const std::vector<std::vector<char>>& map)
: map(map),
_height(static_cast<int>(map.size())),
_width(map.empty() ? 0 : static_cast<int>(map[0].size())) {}
static auto unreachable() -> int { return UNREACHABLE; }
static auto normal_cost() -> int { return NORMAL_COST; }
static auto vortex_cost() -> int { return VORTEX_COST; }
auto cost(const vertex_t& u, const vertex_t& v) const -> int {
auto [ux, uy] = u;
auto [vx, vy] = v;
auto md = std::abs(ux - vx) + std::abs(uy - vy);
switch (md) {
// u = v; staying on the same cell
case 0:
return 0;
// u and v are neighbours
case 1:
break;
// u and v are not neighbouring cells
default:
return UNREACHABLE;
}
// boundary check
if (vy < 0 || vy >= _height || vx < 0 || vx >= _width) {
return UNREACHABLE;
}
switch (map[vy][vx]) {
case '#':
return UNREACHABLE;
case '*':
return VORTEX_COST;
default:
return NORMAL_COST;
}
}
auto width() const -> int { return _width; }
auto height() const -> int { return _height; }
auto has(const vertex_t& v) const -> bool {
auto [x, y] = v;
return (0 <= y && y < _height) && (0 <= x && x < _width);
}
friend std::ostream& operator<<(std::ostream& os, const graph& g);
private:
std::vector<std::vector<char>> map;
int _height, _width;
const static int UNREACHABLE = std::numeric_limits<int>::max();
// XXX: modify here to change the price of entering the vortex
const static int VORTEX_COST = 5;
const static int NORMAL_COST = 1;
};
std::ostream& operator<<(std::ostream& os, const graph& g) {
for (const auto& row : g.map) {
for (const char cell : row) {
os << cell;
}
os << "\n";
}
return os;
}
const static std::vector<vertex_t> DIRECTIONS =
std::vector{std::make_pair(0, 1), std::make_pair(0, -1),
std::make_pair(1, 0), std::make_pair(-1, 0)};
using pqueue_item_t = std::pair<int, vertex_t>;
using pqueue_t = std::vector<pqueue_item_t>;
auto pushq(pqueue_t& q, pqueue_item_t v) -> void {
q.push_back(v);
std::push_heap(q.begin(), q.end(), std::greater<>{});
}
auto popq(pqueue_t& q) -> std::optional<pqueue_item_t> {
if (q.empty()) {
return {};
}
std::pop_heap(q.begin(), q.end(), std::greater<>{});
pqueue_item_t top = q.back();
q.pop_back();
return std::make_optional(top);
}
#endif /* _GRAPH_HPP */