多叉树可以实现复杂的数据结构的存储，通过遍历方法可以方便高效的查找数据，提高查找的效率，同时方便管理节点数据。javascript的DOM其实就是以多叉树的形式存储的。下面用javascript来实现多叉树的数据结构
1、创造一个节点
数据是以节点的形式存储的：
class Node { constructor(data) { this.data = data; this.parent = null; this.children = []; } }
2、创造树
树用来连接节点，就像真实世界树的主干一样，延伸着很多分支
class MultiwayTree { constructor() { this._root = null; } }
3、添加一个节点
function add(data, toData, traversal) { let node = new Node(data) // 第一次添加到根节点 // 返回值为this，便于链式添加节点 if (this._root === null) { this._root = node; return this; } let parent = null, callback = function(node) { if (node.data === toData) { parent = node; return true; } }; // 根据遍历方法查找父节点（遍历方法后面会讲到），然后把节点添加到父节点 // 的children数组里 // 查找方法contains后面会讲到 this.contains(callback, traversal); if (parent) { parent.children.push(node); node.parent = parent; return this; } else { throw new Error('Cannot add node to a non-existent parent.'); } }
4、深度优先遍历
深度优先会尽量先从子节点查找，子节点查找完再从兄弟节点查找，适合数据深度比较大的情况，如文件目录
function traverseDF(callback) { let stack = [], found = false; stack.unshift(this._root); let currentNode = stack.shift(); while(!found && currentNode) { // 根据回调函数返回值决定是否在找到第一个后继续查找 found = callback(currentNode) === true ? true : false; if (!found) { // 每次把子节点置于堆栈最前头，下次查找就会先查找子节点 stack.unshift(...currentNode.children); currentNode = stack.shift(); } } }
5、广度优先遍历
广度优先遍历会优先查找兄弟节点，一层层往下找，适合子项较多情况，如公司岗位级别
function traverseBF(callback) { let queue = [], found = false; queue.push(this._root); let currentNode = queue.shift(); while(!found && currentNode) { // 根据回调函数返回值决定是否在找到第一个后继续查找 found = callback(currentNode) === true ? true : false; if (!found) { // 每次把子节点置于队列最后，下次查找就会先查找兄弟节点 queue.push(...currentNode.children) currentNode = queue.shift(); } } }
6、包含节点
function contains(callback, traversal) { traversal.call(this, callback); }
回调函数算法可自己根据情况实现，灵活度较高
7、移除节点
// 返回被移除的节点 function remove(data, fromData, traversal) { let parent = null, childToRemove = null, callback = function(node) { if (node.data === fromData) { parent = node; return true; } }; this.contains(callback, traversal); if (parent) { let index = this._findIndex(parent.children, data); if (index < 0) { throw new Error('Node to remove does not exist.'); } else { childToRemove = parent.children.splice(index, 1); } } else { throw new Error('Parent does not exist.'); } return childToRemove; }
_findIndex实现:
function _findIndex(arr, data) { let index = -1; for (let i = 0, len = arr.length; i < len; i++) { if (arr[i].data === data) { index = i; break; } } return index; }
完整算法
class Node { constructor(data) { this.data = data; this.parent = null; this.children = []; } } class MultiwayTree { constructor() { this._root = null; } //深度优先遍历 traverseDF(callback) { let stack = [], found = false; stack.unshift(this._root); let currentNode = stack.shift(); while(!found && currentNode) { found = callback(currentNode) === true ? true : false; if (!found) { stack.unshift(...currentNode.children); currentNode = stack.shift(); } } } //广度优先遍历 traverseBF(callback) { let queue = [], found = false; queue.push(this._root); let currentNode = queue.shift(); while(!found && currentNode) { found = callback(currentNode) === true ? true : false; if (!found) { queue.push(...currentNode.children) currentNode = queue.shift(); } } } contains(callback, traversal) { traversal.call(this, callback); } add(data, toData, traversal) { let node = new Node(data) if (this._root === null) { this._root = node; return this; } let parent = null, callback = function(node) { if (node.data === toData) { parent = node; return true; } }; this.contains(callback, traversal); if (parent) { parent.children.push(node); node.parent = parent; return this; } else { throw new Error('Cannot add node to a non-existent parent.'); } } remove(data, fromData, traversal) { let parent = null, childToRemove = null, callback = function(node) { if (node.data === fromData) { parent = node; return true; } }; this.contains(callback, traversal); if (parent) { let index = this._findIndex(parent.children, data); if (index < 0) { throw new Error('Node to remove does not exist.'); } else { childToRemove = parent.children.splice(index, 1); } } else { throw new Error('Parent does not exist.'); } return childToRemove; } _findIndex(arr, data) { let index = -1; for (let i = 0, len = arr.length; i < len; i++) { if (arr[i].data === data) { index = i; break; } } return index; } }
控制台测试代码