這次帶給大家JS數值類型陣列去重，JS數值類型陣列去重的注意事項有哪些，下面就是實戰案例，一起來看一下。
前言
本文主要介紹了關於js建立二元樹進行數值陣列的去重與最佳化的相關內容，分享出來供大家參考學習，下面話不多說了，來一起看看詳細的介紹吧。
常見兩層循環實作數組去重
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)登入後複製
#建立二叉樹實作去重（只適用於數值類型的陣列）
將先前遍歷過的元素，建構成二元樹，樹中每個結點都滿足：左子結點的值< 當前結點的值<右子結點的值
這樣優化了判斷元素是否之前出現過的過程
若元素比目前結點大，只需要判斷元素是否在結點的右子樹中出現過即可
若元素比目前結點小，只需要判斷元素是否在結點的左子樹中出現過即可
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)登入後複製
#優化思路一，記錄最大最小值
記錄已插入元素的最大最小值，若比最大元素大，或最小元素小，則直接插入
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)登入後複製
優化想法二，建立紅黑樹
#建構紅黑樹，平衡樹的高度
有關紅黑樹的部分，請見紅黑樹的插入
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)登入後複製
其他去重方法
#透過Set 物件重新去重
透過sort()
reduce()
方法去重######排序後比較相鄰元素是否相同，若不同則加入到傳回的陣列中#### ##值得注意的是，排序的時候，預設###compare(2, '2') ###回傳0；而reduce() 時，進行全等比較###
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)登入後複製
###透過### 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))
登入後複製
###透過###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
}, [])登入後複製
###透過物件的鍵值對JSON 物件方法去重###
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)))登入後複製
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