2424 *@return {number[] }
2525 */
2626let findOrder = function ( numCourses , prerequisites ) {
27- let prelen = prerequisites . length ,
28- maxNoCircle = numCourses * ( numCourses - 1 ) / 2 ;
29- // 当所有点都有边连接时, 最大的无环边数
30- if ( prelen > maxNoCircle ) {
31- return [ ] ;
32- }
27+ let prelen = prerequisites . length ,
28+ maxNoCircle = numCourses * ( numCourses - 1 ) / 2 ;
29+ // 当所有点都有边连接时, 最大的无环边数
30+ if ( prelen > maxNoCircle ) {
31+ return [ ] ;
32+ }
3333
34- let queue = [ ] , // 存储 BFS 待访问节点序列
35- flags = [ ] , // 存储节点是否被访问过的标记
36- res = [ ] , //结果
37- nodedegree = new Array ( numCourses ) , // 存储node的连边总数
38- edges = new Array ( numCourses ) ; // 存储连边信息, 每个元素中存储的数组表示自己的后续课程
39- for ( let i = 0 ; i < numCourses ; i ++ ) {
40- flags [ i ] = false ;
41- nodedegree [ i ] = 0 ;
42- edges [ i ] = [ ] ;
43- }
34+ let queue = [ ] , // 存储 BFS 待访问节点序列
35+ flags = [ ] , // 存储节点是否被访问过的标记
36+ res = [ ] , //结果
37+ nodedegree = new Array ( numCourses ) , // 存储node的连边总数
38+ edges = new Array ( numCourses ) ; // 存储连边信息, 每个元素中存储的数组表示自己的后续课程
39+ for ( let i = 0 ; i < numCourses ; i ++ ) {
40+ flags [ i ] = false ;
41+ nodedegree [ i ] = 0 ;
42+ edges [ i ] = [ ] ;
43+ }
4444
45- for ( let i = 0 ; i < prelen ; i ++ ) {
46- let source = prerequisites [ i ] [ 0 ] ,
47- target = prerequisites [ i ] [ 1 ] ;
45+ for ( let i = 0 ; i < prelen ; i ++ ) {
46+ let source = prerequisites [ i ] [ 0 ] ,
47+ target = prerequisites [ i ] [ 1 ] ;
4848
49- edges [ target ] . push ( source ) ;
50- nodedegree [ source ] ++ ;
51- nodedegree [ target ] ++ ;
52- }
53-
54- for ( let i = 0 ; i < numCourses ; i ++ ) {
55- if ( nodedegree [ i ] === edges [ i ] . length ) {
56- queue . push ( i ) ;
57- }
58- }
59-
60- if ( bfsVisit ( ) ) {
61- return res ;
62- } else {
63- return [ ] ;
64- }
65-
66- function bfsVisit ( ) {
67- while ( queue . length ) {
68- let current = queue . shift ( ) , //当前访问节点
69- elen = edges [ current ] . length ; // 边数
70-
71- res . push ( current ) ;
72- // console.log(current, res);
73- flags [ current ] = true ;
74- for ( let i = 0 ; i < elen ; i ++ ) {
75- let target = edges [ current ] [ i ] ;
76- if ( flags [ target ] ) {
77- return false ; // 有回路,返回 false
78- }
79- if ( -- nodedegree [ target ] === edges [ target ] . length ) {
80- queue . push ( target ) ;
81- }
82- }
83- edges [ current ] = [ ] ;
84- nodedegree [ current ] -= elen ;
85- }
86-
87- if ( res . length < numCourses ) {
88- return false ;
89- }
90- return true ;
91- }
92- } ;
49+ edges [ target ] . push ( source ) ;
50+ nodedegree [ source ] ++ ;
51+ nodedegree [ target ] ++ ;
52+ }
53+
54+ for ( let i = 0 ; i < numCourses ; i ++ ) {
55+ if ( nodedegree [ i ] === edges [ i ] . length ) {
56+ queue . push ( i ) ;
57+ }
58+ }
59+
60+ if ( bfsVisit ( ) ) {
61+ return res ;
62+ } else {
63+ return [ ] ;
64+ }
65+
66+ function bfsVisit ( ) {
67+ while ( queue . length ) {
68+ let current = queue . shift ( ) , //当前访问节点
69+ elen = edges [ current ] . length ; // 边数
70+
71+ res . push ( current ) ;
72+ // console.log(current, res);
73+ flags [ current ] = true ;
74+ for ( let i = 0 ; i < elen ; i ++ ) {
75+ let target = edges [ current ] [ i ] ;
76+ if ( flags [ target ] ) {
77+ return false ; // 有回路,返回 false
78+ }
79+ if ( -- nodedegree [ target ] === edges [ target ] . length ) {
80+ queue . push ( target ) ;
81+ }
82+ }
83+ edges [ current ] = [ ] ;
84+ nodedegree [ current ] -= elen ;
85+ }
86+
87+ if ( res . length < numCourses ) {
88+ return false ;
89+ }
90+ return true ;
91+ }
92+ } ;