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* PathFinder.cc
*
* Created on: May 30, 2011
* Author: truonghuy
*/
#include <PathFinder.h>
#include <climits>
#include <cmath>
//#include <iostream>
PathFinder::PathFinder() {
// TODO Auto-generated constructor stub
}
/**
*
* @param[in] freeSpace the 2 dimensional array of freeSpace. -1 = obstacle, >=0 free.
* */
int PathFinder::aStar(int startX, int startY, int endX, int endY,
std::vector<std::vector<long> >& freeSpace)
{
int i,j; // counter
std::vector<Node*>::iterator it;
std::vector<Node*> openedList;
std::vector<Node*> closedList;
Node *startNode, *endNode, *currNode;
startNode = new Node();
endNode = new Node();
endNode->x = endX;
endNode->y = endY;
startNode->x = startX;
startNode->y = startY;
startNode->_g = 0;
startNode->_h = manhattanDist(startNode, endNode);
openedList.push_back(startNode);
bool pathFound = false;
while(!openedList.empty()){
std::vector<Node*>::iterator minIndex;
int currCost;
int minCost = INT_MAX;
for (it=openedList.begin(); it < openedList.end(); ++it){
currCost = (*it)->_g + (*it)->_h;
if (minCost > currCost){
minCost = currCost;
minIndex = it;
}
}
// moves the node with min cost from openedList to closedList
currNode = *minIndex;
closedList.push_back(currNode);
openedList.erase(minIndex);
// if finished
if (sameNodes(endNode, currNode)){
endNode->parent = currNode->parent;
pathFound = true;
break;
}
// checks the neighbourhood
int neighborX, neighborY;
Node* node2check;
for(i=-1; i<2; i++){
for(j=-1; j<2; j++){
// only four movement directions
if (fabs(i)+fabs(j) != 1) continue;
neighborX = currNode->x + i;
neighborY = currNode->y + j;
if (neighborX < 0 || neighborY < 0 || neighborX >= freeSpace.size() || neighborY >= freeSpace[0].size())
continue;
// obstacle
if (freeSpace[neighborX][neighborY] < 0) continue;
node2check = new Node();
node2check->x = neighborX;
node2check->y = neighborY;
// if already checked
if (containsNode(openedList, node2check) || containsNode(closedList, node2check)){
delete node2check;
continue;
}
// calculates cost
node2check->_g = currNode->_g + manhattanDist(node2check, currNode);
node2check->_h = manhattanDist(node2check, endNode);
// keep track of path
node2check->parent = currNode;
openedList.push_back(node2check);
}
}
}
if (pathFound){
// go back from endNode
Node *nextNodeFromStart;
nextNodeFromStart = endNode;
int action;
while (!sameNodes(nextNodeFromStart->parent, startNode)){
getAction(startNode, nextNodeFromStart);
nextNodeFromStart = nextNodeFromStart->parent;
}
return getAction(startNode, nextNodeFromStart);
}
else return -1;
};
int PathFinder::getAction(Node* startNode, Node* nextNodeFromStart){
if (startNode->x > nextNodeFromStart->x){
//std::cout << "~left~" << std::endl;
return 3;
}
if (startNode->x < nextNodeFromStart->x){
//std::cout << "~right~" << std::endl;
return 1;
}
if (startNode->y > nextNodeFromStart->y){
//std::cout << "~down~" << std::endl;
return 2;
}
if (startNode->y < nextNodeFromStart->y){
//std::cout << "~up~" << std::endl;
return 4;
}
};
int PathFinder::manhattanDist(Node* startNode, Node* endNode){
return fabs(startNode->x - endNode->x) + fabs(startNode->y - endNode->y);
};
bool PathFinder::sameNodes(Node* node1, Node* node2){
return ((node1->x == node2->x) && (node1->y == node2->y));
};
bool PathFinder::containsNode(std::vector<Node*>& nodeArray, Node* node){
for (unsigned i=0; i<nodeArray.size(); i++){
if (sameNodes(node, nodeArray[i]))
return true;
}
return false;
};
PathFinder::~PathFinder() {
// TODO Auto-generated destructor stub
}
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