functionsum(arr,target){
let left =0,right = arr.length-1while(left<right){
if(arr[left]+arr[right]>target){
right--}elseif(arr[left]+arr[right]<target){
left++}elseif(arr[left]+arr[right]==target){
return[left,right]}}}
2.数组反转
functionreverse(arr){
let left =0, right = arr.length-1while(left < right){
[arr[left],arr[right]]=[arr[right],arr[left]]
left++
right--}return arr
}