120 lines
2.7 KiB
C++
120 lines
2.7 KiB
C++
#ifndef ASTAR_H
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#define ASTAR_H
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#include <iostream>
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#include <vector>
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#include <algorithm>
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#include <limits>
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#include <queue>
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#include <unordered_map>
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#include <cassert>
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#include "../../grid/Grid.h"
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template <typename T> class AStar {
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public:
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//dijkstra with priority queue O(E log V)
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template <typename Access> static std::vector<const T*> get(const T* source, const T* destination, Access acc) {
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// track distances from the source to each other node
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std::unordered_map<const T*, float> distance;
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// track the previous node for each node along the path
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std::unordered_map<const T*, const T*> parent;
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// all nodes
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const std::vector<T>& nodes = acc.getAllNodes();
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// priority queue to check which node is to-be-processed next
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std::priority_queue<std::pair<T*,float>, std::vector<std::pair<const T*,float>>, Comparator2> Q;
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// start with infinite distance
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for(const auto& node : nodes){
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distance[&node] = std::numeric_limits<float>::max();
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}
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// start at the source
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distance[source] = 0.0f;
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Q.push(std::make_pair(source,distance[source]));
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// proceed until there are now new nodes to follow
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while(!Q.empty()) {
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// fetch the next-nearest node from the queue
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const T* u = Q.top().first;
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// and check whether we reached the destination
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if (u == destination) {break;}
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// remove from the Queue
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Q.pop();
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// process all neighbors for the current element
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for( const T& v : acc.getNeighbors(*u)) {
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// weight (distance) between the current node and its neighbor
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//const float w = ((Point3)v - (Point3)*u).length();
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const float w = acc.getWeightBetween(v, *u);
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// found a better route?
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if (distance[&v] > distance[u] + w) {
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distance[&v] = distance[u] + w;
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parent[&v] = u;
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Q.push(std::make_pair(&v, distance[&v] + acc.getHeuristic(v, *source)));
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}
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}
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}
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// construct the path
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std::vector<const T*> path;
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const T* p = destination;
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path.push_back(destination);
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// until we reached the source-node
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while (p!=source) {
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if (p) {
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p = parent[p];
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path.push_back(p);
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} else {
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return std::vector<const T*>(); //if no path could be found, just return an empty vector.
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}
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}
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// done
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return path;
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}
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// template <typename Access> static std::vector<const T*> getShortestPathAStar(const T* src, const T* dst, Access acc){
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// std::vector<const T*> shortestPath;
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// //here we could do some preprocessing. e.g. area of interest of nodes
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// // call aStar
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// shortestPath = aStar(src, dst, acc);
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// return shortestPath;
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// }
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class Comparator2 {
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public:
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int operator() ( const std::pair<const T*,float>& p1, const std::pair<const T*,float>& p2){
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return p1.second > p2.second;
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}
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};
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};
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#endif // ASTAR_H
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