1+ function createCell ( ) {
2+ return {
3+ parent_i : - 1 ,
4+ parent_j : - 1 ,
5+ f : 0.0 ,
6+ g : 0.0 ,
7+ h : 0.0 ,
8+ }
9+ }
10+
11+ function isValid ( grid , row , col ) {
12+ return ( row >= 0 && row < grid . length && col >= 0 && col < grid [ 0 ] . length && ! grid [ row ] [ col ] . isWall ) ;
13+ }
14+
15+ export function aStarSearch ( grid , startRow , startCol , finRow , finCol , checkboxVal ) {
16+ let cellDetails = [ ] ;
17+ let visitedNodesInOrder = [ ] ;
18+
19+ for ( let i = 0 ; i < grid . length ; ++ i ) {
20+ let cell = [ ] ;
21+
22+ for ( let j = 0 ; j < grid [ 0 ] . length ; ++ j )
23+ {
24+ let newCell = createCell ( ) ;
25+ newCell . f = Number . MAX_VALUE ;
26+ newCell . g = Number . MAX_VALUE ;
27+ newCell . h = Number . MAX_VALUE ;
28+ cell . push ( newCell ) ;
29+ }
30+
31+ cellDetails . push ( cell ) ;
32+ }
33+
34+ const i = startRow , j = startCol ;
35+ cellDetails [ i ] [ j ] . f = 0.0 ;
36+ cellDetails [ i ] [ j ] . g = 0.0 ;
37+ cellDetails [ i ] [ j ] . h = 0.0 ;
38+ cellDetails [ i ] [ j ] . parent_i = i ;
39+ cellDetails [ i ] [ j ] . parent_j = j ;
40+ let openList = [ ] ;
41+ openList . push ( [ 0.0 , i , j ] ) ;
42+ var dirx = [ - 1 , 0 , 0 , 1 ] ;
43+ var diry = [ 0 , - 1 , 1 , 0 ] ;
44+
45+ if ( checkboxVal ) {
46+ dirx = [ - 1 , 0 , 0 , 1 , - 1 , - 1 , 1 , 1 ] ;
47+ diry = [ 0 , - 1 , 1 , 0 , - 1 , 1 , - 1 , 1 ] ;
48+ }
49+
50+ while ( openList . length ) {
51+ let i = openList [ 0 ] [ 1 ] , j = openList [ 0 ] [ 2 ] ;
52+ openList . shift ( ) ;
53+ grid [ i ] [ j ] . isVisited = true ;
54+ let gNew , hNew , fNew ;
55+ let newLvl = [ ] ;
56+
57+ // check all possible directions and update the values
58+ for ( let idx = 0 ; idx < dirx . length ; ++ idx ) {
59+ let ii = i + dirx [ idx ] ;
60+ let jj = j + diry [ idx ] ;
61+ const withCheckbox = ( idx < 4 || ( idx > 3 && checkboxVal ) ) ;
62+
63+ if ( isValid ( grid , ii , jj ) && withCheckbox ) {
64+ if ( grid [ ii ] [ jj ] . isFinish ) {
65+ cellDetails [ ii ] [ jj ] . parent_i = i ;
66+ cellDetails [ ii ] [ jj ] . parent_j = j ;
67+ grid [ ii ] [ jj ] . previousNode = grid [ i ] [ j ] ;
68+ if ( newLvl . length ) visitedNodesInOrder . push ( newLvl ) ;
69+ return visitedNodesInOrder ;
70+ }
71+ else if ( ! grid [ ii ] [ jj ] . isVisited ) {
72+ gNew = cellDetails [ i ] [ j ] . g + 1.0 ;
73+ if ( idx > 3 && withCheckbox ) gNew += 0.4 ;
74+ hNew = calculateHValue ( ii , jj , finRow , finCol ) ;
75+ fNew = gNew + hNew ;
76+
77+ if ( cellDetails [ ii ] [ jj ] . f === Number . MAX_VALUE || cellDetails [ ii ] [ jj ] . f > fNew ) {
78+ openList . push ( [ fNew , ii , jj ] ) ;
79+ openList . sort ( ( elemA , elemB ) => elemA [ 0 ] - elemB [ 0 ] ) ;
80+ newLvl . push ( [ ii , jj ] ) ;
81+ cellDetails [ ii ] [ jj ] . f = fNew ;
82+ cellDetails [ ii ] [ jj ] . g = gNew ;
83+ cellDetails [ ii ] [ jj ] . h = hNew ;
84+ cellDetails [ ii ] [ jj ] . parent_i = i ;
85+ cellDetails [ ii ] [ jj ] . parent_j = j ;
86+ grid [ ii ] [ jj ] . previousNode = grid [ i ] [ j ] ;
87+ }
88+ }
89+ }
90+ }
91+
92+ visitedNodesInOrder . push ( newLvl ) ;
93+ }
94+
95+ return visitedNodesInOrder ;
96+ }
97+
98+ // heuristic; approximate distance between current node and finish node
99+ function calculateHValue ( i , j , finRow , finCol ) {
100+ return Math . abs ( finRow - i ) + Math . abs ( finCol - j ) ;
101+ }
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