@@ -29,10 +29,24 @@ BST.prototype.insert = function (value) {
2929}
3030
3131BST . prototype . delete = function ( value ) {
32- // Need help with this one
33- // What would be a good implementation:
34- // All these methods in the Node object
35- // or in the Tree object?
32+ let current = this . search ( value )
33+ 34+ if ( ! current . left )
35+ this . transplant ( current , current . right )
36+ else if ( ! current . right )
37+ this . transplant ( current , current . left )
38+ else {
39+ let y = this . min ( current . right )
40+ 41+ if ( y . parent !== current ) {
42+ this . transplant ( y , y . right )
43+ y . right = current . right
44+ y . right . parent = y
45+ }
46+ this . transplant ( current , y )
47+ y . left = current . left
48+ y . left . parent = y
49+ }
3650}
3751
3852BST . prototype . transplant = function ( u , v ) {
@@ -79,9 +93,8 @@ BST.prototype.sucessor = function(value) {
7993
8094BST . prototype . predecessor = function ( value ) {
8195 let current = this . search ( value )
82- if ( current . left ) {
96+ if ( current . left )
8397 return this . max ( current . left )
84- }
8598 while ( current . parent && current === current . parent . left )
8699 current = current . parent
87100 return current . parent
@@ -131,5 +144,10 @@ test('BST', assert => {
131144 assert . deepEqual ( bst . predecessor ( 12 ) . key , 8 )
132145 assert . deepEqual ( bst . predecessor ( 8 ) . key , 4 )
133146 assert . deepEqual ( bst . predecessor ( 4 ) , null )
147+ bst . delete ( 12 )
148+ assert . deepEqual ( bst . search ( 12 ) , null )
149+ assert . deepEqual ( bst . toArray ( ) , [ 4 , 8 , 15 ] )
150+ assert . deepEqual ( bst . root . left . parent . key , 15 )
151+ assert . deepEqual ( bst . length ( ) , 3 )
134152 assert . end ( )
135153} )
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