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js构建二叉树进行数值数组的去重与优化详解

2024-05-06 16:43:20
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前言

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常见两层循环实现数组去重

let arr = [11, 12, 13, 9, 8, 7, 0, 1, 2, 2, 5, 7, 11, 11, 7, 6, 4, 5, 2, 2]let newArr = []for (let i = 0; i < arr.length; i++) { let unique = true for (let j = 0; j < newArr.length; j++) {  if (newArr[j] === arr[i]) {   unique = false   break  } } if (unique) {  newArr.push(arr[i]) }}console.log(newArr)

构建二叉树实现去重(仅适用于数值类型的数组)

将先前遍历过的元素,构建成二叉树,树中每个结点都满足:左子结点的值 < 当前结点的值 < 右子结点的值

这样优化了判断元素是否之前出现过的过程

若元素比当前结点大,只需要判断元素是否在结点的右子树中出现过即可

若元素比当前结点小,只需要判断元素是否在结点的左子树中出现过即可

let arr = [0, 1, 2, 2, 5, 7, 11, 7, 6, 4,5, 2, 2]class Node { constructor(value) {  this.value = value  this.left = null  this.right = null }}class BinaryTree { constructor() {  this.root = null  this.arr = [] } insert(value) {  let node = new Node(value)  if (!this.root) {   this.root = node   this.arr.push(value)   return this.arr  }  let current = this.root  while (true) {   if (value > current.value) {    if (current.right) {     current = current.right    } else {     current.right = node     this.arr.push(value)     break    }   }   if (value < current.value) {    if (current.left) {     current = current.left    } else {     current.left = node     this.arr.push(value)     break    }   }   if (value === current.value) {    break   }  }  return this.arr }}let binaryTree = new BinaryTree()for (let i = 0; i < arr.length; i++) { binaryTree.insert(arr[i])}console.log(binaryTree.arr)

优化思路一,记录最大最小值

记录已经插入元素的最大最小值,若比最大元素大,或最小元素小,则直接插入

let arr = [11, 12, 13, 9, 8, 7, 0, 1, 2, 2, 5, 7, 11, 11, 7, 6, 4, 5, 2, 2]class Node { constructor(value) {  this.value = value  this.left = null  this.right = null }}class BinaryTree { constructor() {  this.root = null  this.arr = []  this.max = null  this.min = null } insert(value) {  let node = new Node(value)  if (!this.root) {   this.root = node   this.arr.push(value)   this.max = value   this.min = value   return this.arr  }  if (value > this.max) {   this.arr.push(value)   this.max = value   this.findMax().right = node   return this.arr  }  if (value < this.min) {   this.arr.push(value)   this.min = value   this.findMin().left = node   return this.arr  }  let current = this.root  while (true) {   if (value > current.value) {    if (current.right) {     current = current.right    } else {     current.right = node     this.arr.push(value)     break    }   }   if (value < current.value) {    if (current.left) {     current = current.left    } else {     current.left = node     this.arr.push(value)     break    }   }   if (value === current.value) {    break   }  }  return this.arr } findMax() {  let current = this.root  while (current.right) {   current = current.right  }  return current } findMin() {  let current = this.root  while (current.left) {   current = current.left  }  return current }}let binaryTree = new BinaryTree()for (let i = 0; i < arr.length; i++) { binaryTree.insert(arr[i])}console.log(binaryTree.arr)

优化思路二,构建红黑树

构建红黑树,平衡树的高度

有关红黑树的部分,请见红黑树的插入

let arr = [11, 12, 13, 9, 8, 7, 0, 1, 2, 2, 5, 7, 11, 11, 7, 6, 4, 5, 2, 2]console.log(Array.from(new Set(arr)))class Node { constructor(value) {  this.value = value  this.left = null  this.right = null  this.parent = null  this.color = 'red' }}class RedBlackTree { constructor() {  this.root = null  this.arr = [] } insert(value) {  let node = new Node(value)  if (!this.root) {   node.color = 'black'   this.root = node   this.arr.push(value)   return this  }  let cur = this.root  let inserted = false  while (true) {   if (value > cur.value) {    if (cur.right) {     cur = cur.right    } else {     cur.right = node     this.arr.push(value)     node.parent = cur     inserted = true     break    }   }   if (value < cur.value) {    if (cur.left) {     cur = cur.left    } else {     cur.left = node     this.arr.push(value)     node.parent = cur     inserted = true     break    }   }   if (value === cur.value) {    break   }  }  // 调整树的结构  if(inserted){   this.fixTree(node)  }  return this } fixTree(node) {  if (!node.parent) {   node.color = 'black'   this.root = node   return  }  if (node.parent.color === 'black') {   return  }  let son = node  let father = node.parent  let grandFather = father.parent  let directionFtoG = father === grandFather.left ? 'left' : 'right'  let uncle = grandFather[directionFtoG === 'left' ? 'right' : 'left']  let directionStoF = son === father.left ? 'left' : 'right'  if (!uncle || uncle.color === 'black') {   if (directionFtoG === directionStoF) {    if (grandFather.parent) {     grandFather.parent[grandFather.parent.left === grandFather ? 'left' : 'right'] = father     father.parent = grandFather.parent    } else {     this.root = father     father.parent = null    }    father.color = 'black'    grandFather.color = 'red'    father[father.left === son ? 'right' : 'left'] && (father[father.left === son ? 'right' : 'left'].parent = grandFather)    grandFather[grandFather.left === father ? 'left' : 'right'] = father[father.left === son ? 'right' : 'left']    father[father.left === son ? 'right' : 'left'] = grandFather    grandFather.parent = father    return   } else {    grandFather[directionFtoG] = son    son.parent = grandFather    son[directionFtoG] && (son[directionFtoG].parent = father)    father[directionStoF] = son[directionFtoG]    father.parent = son    son[directionFtoG] = father    this.fixTree(father)   }  } else {   father.color = 'black'   uncle.color = 'black'   grandFather.color = 'red'   this.fixTree(grandFather)  } }}let redBlackTree = new RedBlackTree()for (let i = 0; i < arr.length; i++) { redBlackTree.insert(arr[i])}console.log(redBlackTree.arr)

其他去重方法

通过 Set 对象去重

[...new Set(arr)]

通过 sort() + reduce() 方法去重

排序后比较相邻元素是否相同,若不同则添加至返回的数组中

值得注意的是,排序的时候,默认 compare(2, '2') 返回 0;而 reduce() 时,进行全等比较

let arr = [0, 1, 2, '2', 2, 5, 7, 11, 7, 5, 2, '2', 2]let newArr = []arr.sort((a, b) => { let res = a - b if (res !== 0) {  return res } else {  if (a === b) {   return 0  } else {   if (typeof a === 'number') {    return -1   } else {    return 1   }  } }}).reduce((pre, cur) => { if (pre !== cur) {  newArr.push(cur)  return cur } return pre}, null)

通过 includes() + map() 方法去重

let arr = [0, 1, 2, '2', 2, 5, 7, 11, 7, 5, 2, '2', 2]let newArr = []arr.map(a => !newArr.includes(a) && newArr.push(a))

通过 includes() + reduce() 方法去重

let arr = [0, 1, 2, '2', 2, 5, 7, 11, 7, 5, 2, '2', 2]let newArr = arr.reduce((pre, cur) => {  !pre.includes(cur) && pre.push(cur)  return pre}, [])

通过对象的键值对 + JSON 对象方法去重

let arr = [0, 1, 2, '2', 2, 5, 7, 11, 7, 5, 2, '2', 2]let obj = {}arr.map(a => {  if(!obj[JSON.stringify(a)]){    obj[JSON.stringify(a)] = 1  }})console.log(Object.keys(obj).map(a => JSON.parse(a)))

总结

以上就是这篇文章的全部内容了,希望本文的内容对大家的学习或者工作具有一定的参考学习价值,如果有疑问大家可以留言交流,谢谢大家对VeVb武林网的支持。


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