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Refactor BST.

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This commit is contained in:
Oleksii Trekhleb 2018-04-04 09:21:03 +03:00
parent 857edbf3a8
commit 97e6120b3f
4 changed files with 119 additions and 100 deletions
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36
src/data-structures/tree/binary-search-tree/BinarySearchTree.js
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@ -14,41 +14,7 @@ export default class BinarySearchTree {
}
remove(value) {
const nodeToRemove = this.root.find(value);
if (!nodeToRemove) {
throw new Error('Item not found in the tree');
}
const { parent } = nodeToRemove;
if (!nodeToRemove.left && !nodeToRemove.right) {
// Node is a leaf and thus has no children.
// Just remove the pointer to this node from the parent node.
parent.removeChild(nodeToRemove);
} else if (nodeToRemove.left && nodeToRemove.right) {
// Node has two children.
// Find the next biggest value (minimum value in the right branch)
// and replace current value node with that next biggest value.
const nextBiggerNode = nodeToRemove.right.findMin();
if (nextBiggerNode !== nodeToRemove.right) {
this.remove(nextBiggerNode.value);
nodeToRemove.value = nextBiggerNode.value;
} else {
// In case if next right value is the next bigger one and it doesn't have left child
// then just replace node that is going to be deleted with the right node.
nodeToRemove.value = nodeToRemove.right.value;
nodeToRemove.right = nodeToRemove.right.right;
}
} else {
// Node has only one child.
// Make this child to be a direct child of current node's parent.
if (nodeToRemove.left) {
parent.replaceChild(nodeToRemove, nodeToRemove.left);
} else {
parent.replaceChild(nodeToRemove, nodeToRemove.right);
}
}
return this.root.remove(value);
}
toString() {

38
src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js
View File

@ -47,6 +47,44 @@ export default class BinarySearchTreeNode extends BinaryTreeNode {
return !!this.find(value);
}
remove(value) {
const nodeToRemove = this.find(value);
if (!nodeToRemove) {
throw new Error('Item not found in the tree');
}
const { parent } = nodeToRemove;
if (!nodeToRemove.left && !nodeToRemove.right) {
// Node is a leaf and thus has no children.
// Just remove the pointer to this node from the parent node.
parent.removeChild(nodeToRemove);
} else if (nodeToRemove.left && nodeToRemove.right) {
// Node has two children.
// Find the next biggest value (minimum value in the right branch)
// and replace current value node with that next biggest value.
const nextBiggerNode = nodeToRemove.right.findMin();
if (nextBiggerNode !== nodeToRemove.right) {
this.remove(nextBiggerNode.value);
nodeToRemove.value = nextBiggerNode.value;
} else {
// In case if next right value is the next bigger one and it doesn't have left child
// then just replace node that is going to be deleted with the right node.
nodeToRemove.value = nodeToRemove.right.value;
nodeToRemove.right = nodeToRemove.right.right;
}
} else {
// Node has only one child.
// Make this child to be a direct child of current node's parent.
if (nodeToRemove.left) {
parent.replaceChild(nodeToRemove, nodeToRemove.left);
} else {
parent.replaceChild(nodeToRemove, nodeToRemove.right);
}
}
}
findMin() {
if (!this.left) {
return this;

66
src/data-structures/tree/binary-search-tree/__test__/BinarySearchTree.test.js
View File

@ -32,7 +32,7 @@ describe('BinarySearchTree', () => {
expect(bst.contains(40)).toBeFalsy();
});
it('should remove leaf nodes', () => {
it('should remove nodes', () => {
const bst = new BinarySearchTree();
bst.insert(10);
@ -46,68 +46,4 @@ describe('BinarySearchTree', () => {
bst.remove(20);
expect(bst.toString()).toBe('10');
});
it('should remove nodes with one child', () => {
const bst = new BinarySearchTree();
bst.insert(10);
bst.insert(20);
bst.insert(5);
bst.insert(30);
expect(bst.toString()).toBe('5,10,20,30');
bst.remove(20);
expect(bst.toString()).toBe('5,10,30');
bst.insert(1);
expect(bst.toString()).toBe('1,5,10,30');
bst.remove(5);
expect(bst.toString()).toBe('1,10,30');
});
it('should remove nodes with two children', () => {
const bst = new BinarySearchTree();
bst.insert(10);
bst.insert(20);
bst.insert(5);
bst.insert(30);
bst.insert(15);
bst.insert(25);
expect(bst.toString()).toBe('5,10,15,20,25,30');
expect(bst.root.find(20).left.value).toBe(15);
expect(bst.root.find(20).right.value).toBe(30);
bst.remove(20);
expect(bst.toString()).toBe('5,10,15,25,30');
bst.remove(15);
expect(bst.toString()).toBe('5,10,25,30');
bst.remove(10);
expect(bst.toString()).toBe('5,25,30');
expect(bst.root.value).toBe(25);
bst.remove(25);
expect(bst.toString()).toBe('5,30');
bst.remove(5);
expect(bst.toString()).toBe('30');
});
it('should throw error when trying to remove not existing node', () => {
const bst = new BinarySearchTree();
bst.insert(10);
bst.insert(20);
function removeNotExistingElementFromTree() {
bst.remove(30);
}
expect(removeNotExistingElementFromTree).toThrow();
});
});

79
src/data-structures/tree/binary-search-tree/__test__/BinarySearchTreeNode.test.js
View File

@ -92,4 +92,83 @@ describe('BinarySearchTreeNode', () => {
expect(node.find(5)).not.toBeNull();
expect(node.find(5).value).toBe(5);
});
it('should remove leaf nodes', () => {
const bstRootNode = new BinarySearchTreeNode();
bstRootNode.insert(10);
bstRootNode.insert(20);
bstRootNode.insert(5);
expect(bstRootNode.toString()).toBe('5,10,20');
bstRootNode.remove(5);
expect(bstRootNode.toString()).toBe('10,20');
bstRootNode.remove(20);
expect(bstRootNode.toString()).toBe('10');
});
it('should remove nodes with one child', () => {
const bstRootNode = new BinarySearchTreeNode();
bstRootNode.insert(10);
bstRootNode.insert(20);
bstRootNode.insert(5);
bstRootNode.insert(30);
expect(bstRootNode.toString()).toBe('5,10,20,30');
bstRootNode.remove(20);
expect(bstRootNode.toString()).toBe('5,10,30');
bstRootNode.insert(1);
expect(bstRootNode.toString()).toBe('1,5,10,30');
bstRootNode.remove(5);
expect(bstRootNode.toString()).toBe('1,10,30');
});
it('should remove nodes with two children', () => {
const bstRootNode = new BinarySearchTreeNode();
bstRootNode.insert(10);
bstRootNode.insert(20);
bstRootNode.insert(5);
bstRootNode.insert(30);
bstRootNode.insert(15);
bstRootNode.insert(25);
expect(bstRootNode.toString()).toBe('5,10,15,20,25,30');
expect(bstRootNode.find(20).left.value).toBe(15);
expect(bstRootNode.find(20).right.value).toBe(30);
bstRootNode.remove(20);
expect(bstRootNode.toString()).toBe('5,10,15,25,30');
bstRootNode.remove(15);
expect(bstRootNode.toString()).toBe('5,10,25,30');
bstRootNode.remove(10);
expect(bstRootNode.toString()).toBe('5,25,30');
expect(bstRootNode.value).toBe(25);
bstRootNode.remove(25);
expect(bstRootNode.toString()).toBe('5,30');
bstRootNode.remove(5);
expect(bstRootNode.toString()).toBe('30');
});
it('should throw error when trying to remove not existing node', () => {
const bstRootNode = new BinarySearchTreeNode();
bstRootNode.insert(10);
bstRootNode.insert(20);
function removeNotExistingElementFromTree() {
bstRootNode.remove(30);
}
expect(removeNotExistingElementFromTree).toThrow();
});
});