1+ 'use strict' ;
2+ class Node {
3+ constructor ( data ) {
4+ this . data = data ;
5+ this . leftNode = this . rightNode = null ;
6+ }
7+ }
8+ function reverseLevelOrderTraversal ( root ) {
9+ if ( root == null ) return ;
10+ let queue = [ root , null ] ;
11+ let stack = [ null , root , null ] ;
12+ while ( queue . length != 0 ) {
13+ let temp = queue . shift ( ) ;
14+ if ( temp == null ) {
15+ if ( queue . length > 0 ) {
16+ queue . push ( null ) ;
17+ stack . push ( null ) ;
18+ }
19+ } else {
20+ if ( temp . leftNode ) {
21+ queue . push ( temp . leftNode )
22+ stack . push ( temp . leftNode )
23+ }
24+ if ( temp . rightNode ) {
25+ queue . push ( temp . rightNode )
26+ stack . push ( temp . rightNode )
27+ }
28+ }
29+ }
30+ let levelElements = '' ;
31+ while ( stack . length != 0 ) {
32+ let temp = stack . pop ( ) ;
33+ if ( temp == null ) {
34+ console . log ( levelElements ) ;
35+ levelElements = '' ;
36+ } else levelElements = levelElements + temp . data + ' ' ;
37+ }
38+ }
39+ 40+ //level - 1
41+ let tree = new Node ( 1 ) ;
42+ 43+ // level - 2
44+ tree . leftNode = new Node ( 2 ) ;
45+ tree . rightNode = new Node ( 3 ) ;
46+ 47+ // level -3
48+ tree . leftNode . leftNode = new Node ( 4 ) ;
49+ tree . leftNode . rightNode = new Node ( 5 ) ;
50+ 51+ tree . rightNode . leftNode = new Node ( 6 ) ;
52+ tree . rightNode . rightNode = new Node ( 7 ) ;
53+ 54+ // level -4
55+ tree . leftNode . leftNode . leftNode = new Node ( 8 ) ;
56+ tree . leftNode . leftNode . rightNode = new Node ( 9 ) ;
57+ 58+ tree . leftNode . rightNode . leftNode = new Node ( 10 ) ;
59+ tree . leftNode . rightNode . rightNode = new Node ( 11 ) ;
60+ 61+ tree . rightNode . leftNode . leftNode = new Node ( 12 ) ;
62+ tree . rightNode . leftNode . rightNode = new Node ( 13 ) ;
63+ 64+ tree . rightNode . rightNode . leftNode = new Node ( 14 ) ;
65+ tree . rightNode . rightNode . rightNode = new Node ( 15 ) ;
66+ reverseLevelOrderTraversal ( tree ) ;
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