找出数组中重复出现的项

2021-02-26 Javascript

找出数组中重复出现的项

数组中元素为字符串 

function random(){
	return Math.floor(Math.random()*100)
}

let array = Array(1000).fill(1).map(i=>random())
console.time()
let [_,r] = array.reduce((pre,current,index)=>{
	const [list, repeat]=pre;
	if(list.includes(current)){
		repeat[current].push(index)
	}else{
		repeat[current]=[index]
	}
	list.push(current)
	return [list,repeat]
},[[],{}])

let p = Object.entries(r).filter(item=> item[1].length>1)
console.timeEnd()

function random(){
	return Math.floor(Math.random()*100)
}

let array = Array(1000).fill(1).map(i=>random())
console.time()
let [_,r] = array.reduce((pre,current,index)=>{
	const [list, repeat]=pre;
	if(list.includes(current)){
		repeat[current].push(index)
	}else{
		repeat[current]=[index]
	}
	list.push(current)
	return [list,repeat]
},[[],{}])

let p = Object.entries(r).filter(item=> item[1].length>1)
console.timeEnd()

使用生成随机数，用来测试字符串的, 用reduce的性能比较好。

image.png

数组长度为1000000,查找时间为 193ms。

image.png

数组中的元素为对象 

let arr = [
    {name:'小明',age:12,height:88},
    {name:'小明2',age:12,height:58},
    {name:'小明4',age:12,height:28},
    {name:'小明',age:12,height:88},
    {name:'小明',age:12,height:88},
    {name:'小红',age:12,height:88},
    {name:'小红',age:12,height:88},
    {name:'小黄',age:12,height:88},
    {name:'小黄',age:12,height:88},
    {name:'小红',age:12,height:88},
]


let b = arr.reduce((pre, next, index)=>{
    let name = next.name
    if(!pre.hasOwnProperty(name)){
        pre[name] = []
    }
    pre[name].push(index)
    return pre
},{})

let r = Object.entries(b).filter(item=> item[1].length> 1)

let arr = [
    {name:'小明',age:12,height:88},
    {name:'小明2',age:12,height:58},
    {name:'小明4',age:12,height:28},
    {name:'小明',age:12,height:88},
    {name:'小明',age:12,height:88},
    {name:'小红',age:12,height:88},
    {name:'小红',age:12,height:88},
    {name:'小黄',age:12,height:88},
    {name:'小黄',age:12,height:88},
    {name:'小红',age:12,height:88},
]


let b = arr.reduce((pre, next, index)=>{
    let name = next.name
    if(!pre.hasOwnProperty(name)){
        pre[name] = []
    }
    pre[name].push(index)
    return pre
},{})

let r = Object.entries(b).filter(item=> item[1].length> 1)

image.png

找出字符串中出现连续重复的字符 


// *记录连续重复的字符并输出

let s = 'sss11sa22aewqsdasxxssewfdsfwwdgseedffwww';
function search(str) {
  if (str.length === 0) {
    return
  }
  let prev = ''
  let result = []
  let current = ''
  for (let index = 0; index < str.length; index++) {
    const element = str[index];
    if (prev === element) {
      current = current + element
    } else {
      if (current.length) {
        current += prev
        result.push(current);
        current = ''
      }
      prev = element;
    }
  }
 
  return result;
}
 console.log(search(s))


// *记录连续重复的字符并输出

let s = 'sss11sa22aewqsdasxxssewfdsfwwdgseedffwww';
function search(str) {
  if (str.length === 0) {
    return
  }
  let prev = ''
  let result = []
  let current = ''
  for (let index = 0; index < str.length; index++) {
    const element = str[index];
    if (prev === element) {
      current = current + element
    } else {
      if (current.length) {
        current += prev
        result.push(current);
        current = ''
      }
      prev = element;
    }
  }
 
  return result;
}
 console.log(search(s))

符出现的多次的记录 



let a2 = ['s','y','s','s','d','3','y']
let record = {}
for(let i = 0;i< a2.length; i++){
    let key = a2[i]
    if(record[key]){
        record[key].push(i)
    }else{
        record[key] = [i]
    }
}

let recordArray = Object.entries(record).filter((value)=>{
    if(value[1].length>1){
        return {[value[0]]: value[1]}
    }
})

console.log('recordArray',recordArray)

// recordArray [ [ 's', [ 0, 2, 3 ] ], [ 'y', [ 1, 6 ] ] ]



let a2 = ['s','y','s','s','d','3','y']
let record = {}
for(let i = 0;i< a2.length; i++){
    let key = a2[i]
    if(record[key]){
        record[key].push(i)
    }else{
        record[key] = [i]
    }
}

let recordArray = Object.entries(record).filter((value)=>{
    if(value[1].length>1){
        return {[value[0]]: value[1]}
    }
})

console.log('recordArray',recordArray)

// recordArray [ [ 's', [ 0, 2, 3 ] ], [ 'y', [ 1, 6 ] ] ]

更优方案 

let s = 'sss11sa22aewqsdasxxssewfdsfwwdgseedffwww';

function search(str) {
  if (str.length === 0) {
    return
  }
  let prev = ''
  let result = []
  let current = ''
  for (let index = 0; index < str.length; index++) {
    const element = str[index];
    if (prev === element) {
      current = current + element
    } else {
      if (current.length) {
        current += prev
        result.push(current);
        current = ''
      }
      prev = element;
    }
  }
  console.log(result)
  return result;
}

let s = 'sss11sa22aewqsdasxxssewfdsfwwdgseedffwww';

function search(str) {
  if (str.length === 0) {
    return
  }
  let prev = ''
  let result = []
  let current = ''
  for (let index = 0; index < str.length; index++) {
    const element = str[index];
    if (prev === element) {
      current = current + element
    } else {
      if (current.length) {
        current += prev
        result.push(current);
        current = ''
      }
      prev = element;
    }
  }
  console.log(result)
  return result;
}

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