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| 1 Array.prototype.each = function(f) { | |
| 2 if(!f.apply) return; | |
| 3 for(var i=0;i<this.length;i++) { | |
| 4 f.apply(this[i], [i, this]); | |
| 5 } | |
| 6 } | |
| 7 Array.prototype.findGraphNode = function(obj) { | |
| 8 for(var i=0;i<this.length;i++) { | |
| 9 if(this[i].pos == obj.pos) { return this[i]; } | |
| 10 } | |
| 11 return false; | |
| 12 }; | |
| 13 Array.prototype.removeGraphNode = function(obj) { | |
| 14 for(var i=0;i<this.length;i++) { | |
| 15 if(this[i].pos == obj.pos) { this.splice(i,1); } | |
| 16 } | |
| 17 return false; | |
| 18 }; | |
| 19 | |
| 20 function createGraphSet(gridSize, wallFrequency) { | |
| 21 var graphSet = []; | |
| 22 for(var x=0;x<gridSize;x++) { | |
| 23 var row = []; | |
| 24 for(var y=0;y<gridSize;y++) { | |
| 25 // maybe set this node to be wall | |
| 26 var rand = Math.floor(Math.random()*(1/wallFrequency)); | |
| 27 row.push(new GraphNode(x,y,(rand == 0))); | |
| 28 } | |
| 29 graphSet.push(row); | |
| 30 } | |
| 31 return graphSet; | |
| 32 } | |
| 33 | |
| 34 // astar.js | |
| 35 // Implements the astar search algorithm in javascript | |
| 36 | |
| 37 var astar = { | |
| 38 init: function(grid) { | |
| 39 for(var x = 0; x < grid.length; x++) { | |
| 40 for(var y = 0; y < grid[x].length; y++) { | |
| 41 grid[x][y].f = 0; | |
| 42 grid[x][y].g = 0; | |
| 43 grid[x][y].h = 0; | |
| 44 grid[x][y].parent = null; | |
| 45 } | |
| 46 } | |
| 47 }, | |
| 48 search: function(grid, start, end) { | |
| 49 astar.init(grid); | |
| 50 | |
| 51 var openList = []; | |
| 52 var closedList = []; | |
| 53 openList.push(start); | |
| 54 | |
| 55 while(openList.length > 0) { | |
| 56 | |
| 57 // Grab the lowest f(x) to process next | |
| 58 var lowInd = 0; | |
| 59 for(var i=0; i<openList.length; i++) { | |
| 60 if(openList[i].f < openList[lowInd].f) { lowInd = i; } | |
| 61 } | |
| 62 var currentNode = openList[lowInd]; | |
| 63 | |
| 64 // End case -- result has been found, return the traced path | |
| 65 if(currentNode.pos == end.pos) { | |
| 66 var curr = currentNode; | |
| 67 var ret = []; | |
| 68 while(curr.parent) { | |
| 69 ret.push(curr); | |
| 70 curr = curr.parent; | |
| 71 } | |
| 72 return ret.reverse(); | |
| 73 } | |
| 74 | |
| 75 // Normal case -- move currentNode from open to closed, process each
of its neighbors | |
| 76 openList.removeGraphNode(currentNode); | |
| 77 closedList.push(currentNode); | |
| 78 var neighbors = astar.neighbors(grid, currentNode); | |
| 79 | |
| 80 for(var j=0; j<neighbors.length;j++) { | |
| 81 var neighbor = neighbors[j]; | |
| 82 if(closedList.findGraphNode(neighbor) || neighbor.isWall()) { | |
| 83 // not a valid node to process, skip to next neighbor | |
| 84 continue; | |
| 85 } | |
| 86 | |
| 87 // g score is the shortest distance from start to current node,
we need to check if | |
| 88 // the path we have arrived at this neighbor is the shortest o
ne we have seen yet | |
| 89 var gScore = currentNode.g + 1; // 1 is the distance from a node
to it's neighbor | |
| 90 var gScoreIsBest = false; | |
| 91 | |
| 92 | |
| 93 if(!openList.findGraphNode(neighbor)) { | |
| 94 // This the the first time we have arrived at this node, it
must be the best | |
| 95 // Also, we need to take the h (heuristic) score since we ha
ven't done so yet | |
| 96 | |
| 97 gScoreIsBest = true; | |
| 98 neighbor.h = astar.heuristic(neighbor.pos, end.pos); | |
| 99 openList.push(neighbor); | |
| 100 } | |
| 101 else if(gScore < neighbor.g) { | |
| 102 // We have already seen the node, but last time it had a wor
se g (distance from start) | |
| 103 gScoreIsBest = true; | |
| 104 } | |
| 105 | |
| 106 if(gScoreIsBest) { | |
| 107 // Found an optimal (so far) path to this node. Store info
on how we got here and | |
| 108 // just how good it really is... | |
| 109 neighbor.parent = currentNode; | |
| 110 neighbor.g = gScore; | |
| 111 neighbor.f = neighbor.g + neighbor.h; | |
| 112 } | |
| 113 } | |
| 114 } | |
| 115 | |
| 116 // No result was found -- empty array signifies failure to find path | |
| 117 return []; | |
| 118 }, | |
| 119 heuristic: function(pos0, pos1) { | |
| 120 // This is the Manhattan distance | |
| 121 var d1 = Math.abs (pos1.x - pos0.x); | |
| 122 var d2 = Math.abs (pos1.y - pos0.y); | |
| 123 return d1 + d2; | |
| 124 }, | |
| 125 neighbors: function(grid, node) { | |
| 126 var ret = []; | |
| 127 var x = node.pos.x; | |
| 128 var y = node.pos.y; | |
| 129 | |
| 130 if(grid[x-1] && grid[x-1][y]) { | |
| 131 ret.push(grid[x-1][y]); | |
| 132 } | |
| 133 if(grid[x+1] && grid[x+1][y]) { | |
| 134 ret.push(grid[x+1][y]); | |
| 135 } | |
| 136 if(grid[x][y-1] && grid[x][y-1]) { | |
| 137 ret.push(grid[x][y-1]); | |
| 138 } | |
| 139 if(grid[x][y+1] && grid[x][y+1]) { | |
| 140 ret.push(grid[x][y+1]); | |
| 141 } | |
| 142 return ret; | |
| 143 } | |
| 144 }; | |
| 145 | |
| 146 function go() { | |
| 147 path = astar.search(g1, start, end); | |
| 148 }; | |
| 149 | |
| 150 go(); | |
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