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Commit afa4948

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Simplify AVL tree node deletion.
1 parent 04e533e commit afa4948

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2 files changed

+72
-87
lines changed

2 files changed

+72
-87
lines changed

‎src/data-structures/tree/avl-tree/AvlTree.js‎

Lines changed: 5 additions & 56 deletions
Original file line numberDiff line numberDiff line change
@@ -16,54 +16,16 @@ export default class AvlTree extends BinarySearchTree {
1616
}
1717
}
1818

19-
remove(value) {
20-
const nodeToRemove = this.root.find(value);
21-
22-
if (!nodeToRemove) {
23-
throw new Error('Item not found in the tree');
24-
}
25-
26-
// Recursively find target node, if found then delete and balance.
27-
// return nodeToRemove.value;
28-
this.root = this.removeRecv(this.root, nodeToRemove);
29-
}
30-
31-
removeRecv(origin, node) {
32-
let newOrigin = origin;
33-
if (origin.value > node.value) {
34-
// Recursively traversing from left
35-
newOrigin.left = this.removeRecv(origin.left, node);
36-
} else if (origin.value < node.value) {
37-
// Recursively traversing from right
38-
newOrigin.right = this.removeRecv(origin.right, node);
39-
} else {
40-
if (origin.left == null) {
41-
// Forget right node
42-
return origin.right;
43-
}
44-
if (origin.right == null) {
45-
// Forget left node
46-
return origin.left;
47-
}
48-
49-
// Recursively find min node from left subtree
50-
// more efficient traversing
51-
const parent = Object.assign({}, origin);
52-
newOrigin = parent.right.findMin();
53-
newOrigin.right = this.deleteMin(parent.right);
54-
newOrigin.left = parent.left;
55-
}
56-
57-
// Balance and return root node
58-
return this.balance(newOrigin);
59-
}
60-
6119
/**
6220
* @param {*} value
6321
* @return {boolean}
6422
*/
6523
remove(value) {
66-
throw new Error(`Can't remove ${value}. Remove method is not implemented yet`);
24+
// Do standard BST removal.
25+
super.remove(value);
26+
27+
// Balance the tree starting from the root node.
28+
this.balance(this.root);
6729
}
6830

6931
/**
@@ -90,8 +52,6 @@ export default class AvlTree extends BinarySearchTree {
9052
this.rotateRightLeft(node);
9153
}
9254
}
93-
// Return the heap to avoid referenceError
94-
return node;
9555
}
9656

9757
/**
@@ -200,15 +160,4 @@ export default class AvlTree extends BinarySearchTree {
200160
// Attach rootNode to the left of rightNode.
201161
rightNode.setLeft(rootNode);
202162
}
203-
204-
deleteMin(node) {
205-
// Forget right node if has value
206-
if (node.left == null) return node.right;
207-
208-
const newNode = node;
209-
newNode.left = this.deleteMin(node.left);
210-
211-
// Balance and return root node
212-
return this.balance(newNode);
213-
}
214163
}

‎src/data-structures/tree/avl-tree/__test__/AvlTRee.test.js‎

Lines changed: 67 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -186,31 +186,6 @@ describe('AvlTree', () => {
186186
expect(tree.toString()).toBe('6,8,9,18,21,22,43');
187187
});
188188

189-
it('should keep balance after removal', () => {
190-
const tree = new AvlTree();
191-
192-
tree.insert(1);
193-
tree.insert(2);
194-
tree.insert(3);
195-
tree.insert(4);
196-
tree.insert(5);
197-
tree.insert(6);
198-
tree.insert(7);
199-
tree.insert(8);
200-
tree.insert(9);
201-
202-
expect(tree.toString()).toBe('1,2,3,4,5,6,7,8,9');
203-
expect(tree.root.height).toBe(3);
204-
205-
tree.remove(8);
206-
tree.remove(9);
207-
208-
expect(tree.contains(8)).toBeFalsy();
209-
expect(tree.contains(9)).toBeFalsy();
210-
expect(tree.toString()).toBe('1,2,3,4,5,6,7');
211-
expect(tree.root.height).toBe(2);
212-
});
213-
214189
it('should do left right rotation and keeping left right node safe', () => {
215190
const tree = new AvlTree();
216191

@@ -255,13 +230,74 @@ describe('AvlTree', () => {
255230
expect(tree.root.height).toBe(3);
256231
});
257232

258-
it('should throw an error when trying to remove the node', () => {
259-
const removeNodeAvlTree = () => {
260-
const tree = new AvlTree();
233+
it('should remove values from the tree with right-right rotation', () => {
234+
const tree = new AvlTree();
235+
236+
tree.insert(10);
237+
tree.insert(20);
238+
tree.insert(30);
239+
tree.insert(40);
240+
241+
expect(tree.toString()).toBe('10,20,30,40');
242+
243+
tree.remove(10);
244+
245+
expect(tree.toString()).toBe('20,30,40');
246+
expect(tree.root.value).toBe(30);
247+
expect(tree.root.left.value).toBe(20);
248+
expect(tree.root.right.value).toBe(40);
249+
expect(tree.root.balanceFactor).toBe(0);
250+
});
251+
252+
it('should remove values from the tree with left-left rotation', () => {
253+
const tree = new AvlTree();
254+
255+
tree.insert(10);
256+
tree.insert(20);
257+
tree.insert(30);
258+
tree.insert(5);
259+
260+
expect(tree.toString()).toBe('5,10,20,30');
261+
262+
tree.remove(30);
263+
264+
expect(tree.toString()).toBe('5,10,20');
265+
expect(tree.root.value).toBe(10);
266+
expect(tree.root.left.value).toBe(5);
267+
expect(tree.root.right.value).toBe(20);
268+
expect(tree.root.balanceFactor).toBe(0);
269+
});
270+
271+
it('should keep balance after removal', () => {
272+
const tree = new AvlTree();
273+
274+
tree.insert(1);
275+
tree.insert(2);
276+
tree.insert(3);
277+
tree.insert(4);
278+
tree.insert(5);
279+
tree.insert(6);
280+
tree.insert(7);
281+
tree.insert(8);
282+
tree.insert(9);
283+
284+
expect(tree.toString()).toBe('1,2,3,4,5,6,7,8,9');
285+
expect(tree.root.value).toBe(4);
286+
expect(tree.root.height).toBe(3);
287+
expect(tree.root.balanceFactor).toBe(-1);
288+
289+
tree.remove(8);
261290

262-
tree.remove(1);
263-
};
291+
expect(tree.root.value).toBe(4);
292+
expect(tree.root.balanceFactor).toBe(-1);
293+
294+
tree.remove(9);
264295

265-
expect(removeNodeAvlTree).toThrowError();
296+
expect(tree.contains(8)).toBeFalsy();
297+
expect(tree.contains(9)).toBeFalsy();
298+
expect(tree.toString()).toBe('1,2,3,4,5,6,7');
299+
expect(tree.root.value).toBe(4);
300+
expect(tree.root.height).toBe(2);
301+
expect(tree.root.balanceFactor).toBe(0);
266302
});
267303
});

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