perlin_noise/dijkstra.js

//implemtantion of dijkstra algorithm


var max = Number.MAX_SAFE_INTEGER-100;


function findNodeWithMinDistAndInQ(list, Q){
	var result = "NaN";
	var dist = max;
	for(var i = 0; i < Q.length; i++){
		//console.log(Q[i]);
		if(list.get(Q[i]) < dist){
			dist = list.get(Q[i]);
			result = Q[i];
		}
	}
	//console.log("result: "+result);
	return result;
}

function getNeighbours(array, i,j){
	var result = [];
	if((i-1) > -1 && (i+1) < array.length && (j-1) > -1 && j+1 < array[i].length){
		for(var k = -1; k < 2; k++){
			for(var l = -1; l < 2; l++){
				var row =i+k;
				var coloumn=j+l; 
				if(array[row][coloumn].accessible){
					result.push(row+"$"+coloumn);
				}
			}	
		}	
	} else {

		for(var k = -1; k < 2; k++){
			for(var l = -1; l < 2; l++){
				var row =i+k;
				var coloumn=j+l; 
				try{
					if(array[row][coloumn].accessible){
						result.push(row+"$"+coloumn);
					}
				} catch(e){
					////console.log("zugriff auserhalb des feldes");	
				}
			}	
		}
	}

	return result;
}


/**
 *
 */
function dijkstra(array, start_i, start_j, end_i,end_j){

	var Q = [];
	var distance = new Map();
	var pre = new Map();
		

	for(var i = 0; i < array.length; i++){
		for(var j = 0; j < array[i].length; j++){
			var tmp = i+"$"+j; 
			distance.set(tmp, max);
			pre.set(tmp, null);
			Q.push(tmp);
		}
	}

	distance.set(start_i+"$"+start_j, 0);
	var t = 0;	
	while (Q.length !== 0){
		var node = findNodeWithMinDistAndInQ(distance,Q);
		if(node === "NaN"){
			console.log(Q);
			console.log(distance);
			
			return null;
		}

		Q.splice(Q.indexOf(node),1);
		var indices = node.split("$");
		indices[0] = parseInt(10, indices[0]);
		indices[1] = parseInt(10, indices[1]);

		var neighbours = getNeighbours(array,indices[0],indices[1]);
		//console.log(node+" === "+end_i+"$"+end_j);

		if(node.localeCompare(end_i+"$"+end_j) === 0){

			console.log("YAY");
			
			console.log(t);
			console.log(distance);
			console.log(pre);

			
			
			return reverse(end_i+"$"+end_j,start_i+"$"+start_j,pre);
		}
		for(var i = 0; i < neighbours.length; i++){
			var alt = distance.get(node)+1;

			if(Q.includes(neighbours[i])){
				if(alt < distance.get(neighbours[i])){
					distance.set(neighbours[i], alt);
					pre.set(neighbours[i],  node);
				}
			}
		}
		//console.log(t);
		t++;
	}//

	console.log(t);
	console.log(distance);
	console.log(pre);

	return null; 

}

function reverse(target, source, pre){
	var path = [];
	var u = target;
	
	console.log("target: "+target);
	console.log("source: "+source);
	if(pre.get(u) != null || u === source){
		console.log("hallo");
		while(u != null){
			console.log("hallo");
			u = pre.get(u);
			path = [u].concat(path);	
		}
	}
	path.push(target);
	path.shift();
	
	
	console.log("!!!!")
	console.log(path);
	
	return path;
	
	
}