二分查找

  1. function binary_search(arr,low,high,key){
  2.   if(low>high){
  3.     return -1
  4.   }
  5.   let mid = Math.floor((high+low)/2)
  6.   if(arr[mid]=key){
  7.     return mid
  8.   }else if(arr[mid]>key){
  9.     high=mid-1
  10.     return binary_search(arr,low,high,key)
  11.   }else if(arr[mid]<key){
  12.     low=mid+1
  13.     return binary_search(arr,low,high,key)
  14.   }  
  15. }