perlin_noise/dijkstra.js

//implemtantion of dijkstra algorithm


var max = Number.MAX_SAFE_INTEGER;


function findNodeWithMinDist(list){
	var result = "";
	var dist = max;
	for(var i = 0; i < list.length; i++){
		for(var j = 0; j < list[i].length; j++){
			if(dist < list[i][j]){
				dist = list[i][j];
				result = i+"$"+j;
			}
		}
	}

	return result;
}

function getNeighbours(array, i,j){
	var result = [];
	if(i - 1 > -1 && i+1 < array.length){ 
		if(j-1 > -1 && j+1 < array.length){
			for(var k = -1; k < 2; k++){
				for(var l = -1; l < 2; l){
					if(array[i][j].accessible){
						result.push(i+"$"+j);
					}
				}	
			}
		}
	} else {
		for(var k = -1; k < 2; k++){
			for(var l = -1; l < 2; l){
				try{
					if(array[i][j].accessible){
						result.push(i+"$"+j);
					}
				} catch(e){
					console.log("zugriff auserhalb des feldes");	
				}
			}	
		}
	}

	return result;
}


/**
 *
 */
function dijkstra(array, start_i, start_j, end_i,end_j){
	var Q = new Set();
	var distance = [];
	var pre = [];
	

	for(var i = 0; i < array.length; i++){
		for(var j = 0; j < array[i].length; j++){
			distance[i][j] = max;
			pre[i][j] = null;
			Q.add(i+"$"+j);
		}
	}
	distance[start_i][start_j] = 0;
	
	while !(Q.size === 0){
		var node = findNodeWithMinDist(distance);
		Q.delete(node);
		var indices = node.split("$");
		var neighbours = getNeighbours(array,indicies[0],indices[1]);
		for(var i = 0; i < indices.length; i++){
			var alt = dist[indices[0]][indices[1]]+1;
			if(Q.has(neighbours[i])){
				var indices_neighbour = neighbour[i].split("$");
				if(alt < dist[indices_neighbour[i]][indices_neighbour[j]]){
					dist[indicies_neighbour[i]][indices_neighbour[j]] = alt;
					pre[indices_neighbour[i]][indices_neighbour[j]] = node;
				}
			}
		}
	}




	return {dist: distance[], pre: pre[]}; 

}