找出数组 中只出现一次的 元素 多种写法
function SingleNumber1(nums){
for(let i = 0; i < arr.length; i++) {
{
let c=JSON.parse(JSON.stringify(nums))
c.splice(i,1)
if(!c.includes(nums[i])){
console.log(nums[i],i);
return nums[i]
}
}
}
function getSingle2(arr) {
let newList=[]
for(let i = 0; i < arr.length; i++) {
if(arr.indexOf(arr[i])==arr.lastIndexOf(arr[i])){
newList.push( arr[i])
}
}
console.log(newList)
}
unction getSingle3(arr){
let c=null
for (let i=0; i<arr.length; i++){
let b=0;
for(let j = 0; j < arr.length; j++) {
if(arr[i]==arr[j]){
c=arr[i];
b++;
if(b==2){
c=null
continue
}
}
}
if(b==1){
console.log(c)
break
}
}
}
function getSingle4(arr){
let map=new Map()
for(let i in arr){
if(!map[arr[i]]){
map[arr[i]]=1
}else{
map[arr[i]]++
}
}
for(let i in map){
if(map[i]==1){
console.log(i)
}
}
}
function getSingle5(arr) {
console.time("test")
let counts={}
for (let num of arr) {
counts[num] = counts[num] ? counts[num] + 1 : 1;
}
for (let num in counts) {
if(counts[num]==1){
console.log(counts[num])
break
}
}
console.timeEnd("test")
}
const arr = [1,3,2,4, 3, 2, 2, 1,11,11];
