mgs/a-star-maze-solver
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Algorithm works

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This commit is contained in:
karl 2020-10-15 11:05:48 +02:00
parent 5ffbef59a8
commit b16f9a356a
1 changed files with 40 additions and 25 deletions
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65
main.cpp
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@ -9,11 +9,9 @@ struct Maze {
}; };
struct MazeNode { struct MazeNode {
MazeNode(uint x, uint y, uint cost, uint travelled) : x(x), y(y), cost(cost), travelled(travelled) {} MazeNode(std::vector<uint> v, uint priority) : v(v), priority(priority) {}
uint x; std::vector<uint> v;
uint y; uint priority;
uint cost;
uint travelled;
}; };
Maze solve_maze(const Maze &maze) { Maze solve_maze(const Maze &maze) {
@ -22,49 +20,66 @@ Maze solve_maze(const Maze &maze) {
result = maze; result = maze;
std::vector<MazeNode> nodes; std::vector<MazeNode> nodes;
std::make_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.cost > n2.cost;}); std::make_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.priority > n2.priority;});
nodes.push_back(MazeNode(1, 1)); nodes.push_back(MazeNode(std::vector<uint>{1, 1}, 0));
std::push_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.cost > n2.cost;}); std::push_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.priority > n2.priority;});
std::map<MazeNode, uint> costs; std::map<std::vector<uint>, uint> costs;
std::map<MazeNode, MazeNode> parents; std::map<std::vector<uint>, std::vector<uint>> parents;
for (int i = 0; i < 5000; i++) { costs[std::vector<uint>{1, 1}] = 1;
for (int i = 0; i < 270; i++) {
// Get the best node // Get the best node
MazeNode best = nodes.front(); MazeNode best = nodes.front();
std::pop_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.cost > n2.cost;}); std::pop_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.priority > n2.priority;});
nodes.pop_back(); nodes.pop_back();
int current_x = best.x; int current_x = best.v[0];
int current_y = best.y; int current_y = best.v[1];
std::vector<uint> here = std::vector<uint>{current_x, current_y};
result.data[current_y][current_x] = 'P'; result.data[current_y][current_x] = 'P';
std::cout << i << ": " << current_x << ", " << current_y << " with " << best.travelled << " travelled" << " and cost " << best.cost << std::endl; std::cout << i << ": " << current_x << ", " << current_y << " with " << " and priority " << best.priority << std::endl;
// The cost is the travelled distance to the next node
uint cost = costs[here] + 1;
for (int kernel_y = -1; kernel_y <= 1; kernel_y++) { for (int kernel_y = -1; kernel_y <= 1; kernel_y++) {
for (int kernel_x = -1; kernel_x <= 1; kernel_x++) { for (int kernel_x = -1; kernel_x <= 1; kernel_x++) {
// Ignore the current position // Ignore the current position
if (kernel_x == 0 && kernel_y == 0) continue; if (kernel_x == 0 && kernel_y == 0) continue;
int x = current_x + kernel_x; uint x = current_x + kernel_x;
int y = current_y + kernel_y; uint y = current_y + kernel_y;
// Can we go here? // Can we go here?
if (maze.data[y][x] == '#') continue; if (maze.data[y][x] == '#') continue;
// The cost is the already travelled distance together with the optimal // Are we done?
// distance from here to the target if (x == 39 && y == 39) {
uint cost = best.travelled + 1 + (39 - x) + (39 - y); return result;
}
// Add this node std::vector<uint> next = std::vector<uint>{x, y};
nodes.push_back(MazeNode(x, y, cost, best.travelled + 1));
std::push_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.cost > n2.cost;}); // If this node hasn't been added yet or its costs are better, add it!
if (costs.find(next) == costs.end() || cost < costs[next]) {
costs[next] = cost;
uint priority = cost + (39 - x) + (39 - y);
std::cout << x << ", " << y << ": Adding node with priority " << priority << std::endl;
// Add this node
nodes.push_back(MazeNode(next, priority));
std::push_heap(nodes.begin(), nodes.end(), [](MazeNode n1, MazeNode n2){return n1.priority > n2.priority;});
parents[next] = here;
}
} }
} }
std::cout << nodes.size() << std::endl;
} }
return result; return result;