js构建二叉树进行数值数组的去重与优化详解

前言

本文主要介绍了关于js构建二叉树进行数值数组的去重与优化的相关内容，分享出来供大家参考学习，下面话不多说了，来一起看看详细的介绍吧。

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

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，谢谢大家对的支持。