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/*
* TDDD86 Lab 8 - gusso230 (group 11)
* This file contains implementations of DFS, BFS, Dijkstra's algorithm and A*.
*
* NOTE The UI sometimes hangs when calling setColor on a node.
*/
#include "costs.h"
#include "trailblazer.h"
#include <stack>
#include <queue>
#include <vector>
#include <algorithm>
#include <limits>
#include "pqueue.h"
using namespace std;
/*
* Construct a path from end by recursively adding and following node.previous.
*/
vector<Node*> path_from_end(Node* end, bool color_green = false) {
if (!end->previous) {
// no more nodes to follow
return {};
}
Node* cur = end;
vector<Node*> path;
while (cur) {
if (color_green) {
cur->setColor(GREEN);
}
path.push_back(cur);
cur = cur->previous;
}
reverse(path.begin(), path.end());
return path;
}
/*
* push_back all items from 'from' to 'to'.
*/
template <typename T>
void push_back_from(vector<T>& to, const vector<T>& from) {
for (const auto& el : from) {
to.push_back(el);
}
}
/*
* Recursively find a path from start to end with DFS.
*/
vector<Node*> dfs_helper(BasicGraph& graph, Vertex* start, Vertex* end) {
start->setColor(GREEN);
vector<Node*> path = { start };
if (start == end) {
return path;
}
start->visited = true;
for (const auto& arc : start->arcs) {
if (!arc->finish->visited) {
vector<Node*> neighbour_path = dfs_helper(graph, arc->finish, end);
if (neighbour_path.size() == 0) {
continue;
}
vector<Node*> new_path(path);
push_back_from(new_path, neighbour_path);
return new_path;
}
}
start->setColor(GRAY);
return {};
}
/*
* Find any path from start to end with DFS.
*/
vector<Node*> depthFirstSearch(BasicGraph& graph, Vertex* start, Vertex* end) {
graph.resetData();
return dfs_helper(graph, start, end);
}
/*
* Find a path from start to end with BFS.
*
* The path found will have the least amount of steps, but ignores edge weights.
*/
vector<Node *> breadthFirstSearch(BasicGraph& graph, Vertex* start, Vertex* end) {
graph.resetData();
queue<Node*> q;
q.push(start);
start->visited = true;
while (q.size() > 0) {
Node* cur = q.front();
q.pop();
cur->setColor(GREEN);
if (cur == end) {
break;
}
for (const auto& arc : cur->arcs) {
if (!arc->finish->visited) {
arc->finish->visited = true;
arc->finish->previous = cur;
arc->finish->setColor(YELLOW);
q.push(arc->finish);
}
}
}
return path_from_end(end);
}
/*
* Find a path from start to end with Dijkstra's algorithm.
*
* The path found will have the smallest total weight in a terrain and
* the least amount of steps in a maze.
*/
vector<Node*> dijkstrasAlgorithm(BasicGraph& graph, Vertex* start, Vertex* end) {
graph.resetData();
PriorityQueue<Node *> q;
q.enqueue(start, 0.0);
start->visited = true;
while (q.size() > 0) {
Node* cur = q.dequeue();
cur->visited = true;
// we have found the shortest path here so color as green
cur->setColor(GREEN);
if (cur == end) {
// all nodes in q have 'previous' set to we can follow it all the way to start
break;
}
for (const auto& arc : cur->arcs) {
if (!arc->finish->visited) {
double new_dist = arc->start->cost + arc->cost;
if (arc->finish->cost == 0.0) {
// this is the first time we queue this node
arc->finish->previous = cur;
arc->finish->cost = new_dist;
arc->finish->setColor(YELLOW);
q.enqueue(arc->finish, new_dist);
}
else if (new_dist < arc->finish->cost) {
// we have queued this before but have now found a cheaper path
arc->finish->previous = cur;
arc->finish->cost = new_dist;
q.changePriority(arc->finish, new_dist);
}
}
}
}
return path_from_end(end);
}
/*
* Find a path from start to end with A*.
*
* The path found will have the smallest total weight in a terrain and
* the least amount of steps in a maze.
*/
vector<Node*> aStar(BasicGraph& graph, Vertex* start, Vertex* end) {
graph.resetData();
PriorityQueue<Node *> q;
q.enqueue(start, 0.0);
start->visited = true;
while (q.size() > 0) {
Node* cur = q.dequeue();
cur->visited = true;
// we have found the shortest path here so color as green
cur->setColor(GREEN);
if (cur == end) {
// all nodes in q have 'previous' set to we can follow it all the way to start
break;
}
for (const auto& arc : cur->arcs) {
if (!arc->finish->visited) {
double new_dist = arc->start->cost + arc->cost;
if (arc->finish->cost == 0.0) {
// this is the first time we queue this node
arc->finish->previous = cur;
arc->finish->cost = new_dist;
arc->finish->setColor(YELLOW);
q.enqueue(arc->finish, new_dist + arc->finish->heuristic(end));
}
else if (new_dist < arc->finish->cost) {
// we have queued this before but have now found a cheaper path
arc->finish->previous = cur;
arc->finish->cost = new_dist;
q.changePriority(arc->finish, new_dist + arc->finish->heuristic(end));
}
}
}
}
return path_from_end(end);
}
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