|
| 1 | +// https://en.wikipedia.org/wiki/Binary_search_tree |
| 2 | + |
| 3 | +function Node(data) { |
| 4 | + this.key = data |
| 5 | + this.left = null |
| 6 | + this.right = null |
| 7 | +} |
| 8 | + |
| 9 | +function BST() { |
| 10 | + this.root = null |
| 11 | +} |
| 12 | + |
| 13 | +BST.prototype.insert = function (value) { |
| 14 | + let node = new Node(value), |
| 15 | + current = null, |
| 16 | + x = this.root |
| 17 | + |
| 18 | + while (x !== null) { |
| 19 | + current = x |
| 20 | + if (node.key < x.key) x = x.left |
| 21 | + else x = x.right |
| 22 | + } |
| 23 | + |
| 24 | + if (current === null) this.root = node |
| 25 | + else if (node.key < current.key) current.left = node |
| 26 | + else current.right = node |
| 27 | +} |
| 28 | + |
| 29 | +BST.prototype.delete = function (value) { |
| 30 | + // Need help with this one, as most other languages implementations |
| 31 | + // depend on the parent being stored in the node |
| 32 | + // Is there another way of traversing the three in O(lg n) without |
| 33 | + // that? |
| 34 | + let current = this.root, |
| 35 | + parent = null, |
| 36 | + found = false |
| 37 | + |
| 38 | + while (!found && current) { |
| 39 | + parent = current |
| 40 | + if (value < current.key) current = current.left |
| 41 | + else if (value > current.key) current = current.right |
| 42 | + else found = true |
| 43 | + } |
| 44 | + |
| 45 | + if (!found) return |
| 46 | + |
| 47 | + // delete a node with no children |
| 48 | + // if (!current.left || !current.right) { |
| 49 | + // if (current === parent.left) { |
| 50 | + // parent.left = current.left || current.right |
| 51 | + // if (!parent.left) { |
| 52 | + // parent.left.parent = parent |
| 53 | + // } |
| 54 | + // } |
| 55 | + // } |
| 56 | +} |
| 57 | + |
| 58 | +BST.prototype.search = function (value) { |
| 59 | + let current = this.root |
| 60 | + while (current) { |
| 61 | + if (value === current.key) return current |
| 62 | + else if (value < current.key) current = current.left |
| 63 | + else current = current.right |
| 64 | + } |
| 65 | + return null |
| 66 | +l} |
| 67 | + |
| 68 | +BST.prototype.min = function () { |
| 69 | + let current = this.root.left |
| 70 | + while (current.left) current = current.left |
| 71 | + return current |
| 72 | +} |
| 73 | + |
| 74 | +BST.prototype.max = function () { |
| 75 | + let current = this.root.right |
| 76 | + while (current.right) current = current.right |
| 77 | + return current |
| 78 | +} |
| 79 | + |
| 80 | +BST.prototype.length = function () { |
| 81 | + let count = 0 |
| 82 | + this.inorderTreeWalk(this.root, function() { |
| 83 | + count++ |
| 84 | + }) |
| 85 | + return count |
| 86 | +} |
| 87 | + |
| 88 | +BST.prototype.toArray = function () { |
| 89 | + let result = [] |
| 90 | + this.inorderTreeWalk(this.root, function(key) { |
| 91 | + result.push(key) |
| 92 | + }) |
| 93 | + return result |
| 94 | +} |
| 95 | + |
| 96 | +BST.prototype.inorderTreeWalk = function (node, callback) { |
| 97 | + if (node) { |
| 98 | + this.inorderTreeWalk(node.left, callback) |
| 99 | + callback(node.key) |
| 100 | + this.inorderTreeWalk(node.right, callback) |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +const test = require('tape') |
| 105 | + |
| 106 | +test('BST', assert => { |
| 107 | + let bst = new BST() |
| 108 | + bst.insert(12) |
| 109 | + bst.insert(4) |
| 110 | + bst.insert(8) |
| 111 | + bst.insert(15) |
| 112 | + assert.deepEqual(bst.search(15).key, 15) |
| 113 | + assert.deepEqual(bst.min().key, 4) |
| 114 | + assert.deepEqual(bst.max().key, 15) |
| 115 | + assert.deepEqual(bst.toArray(), [4,8,12,15]) |
| 116 | + assert.deepEqual(bst.length(), 4) |
| 117 | + assert.end() |
| 118 | +}) |
0 commit comments