1. 前提条件：一个有序的数组
   const arr=[ 33, 44, 55, 55, 78, 88, 99, 101, 110, 115, 120, 125, 130, 140, 150, 166 ];

2. 问题：查找其中是否包含指定数字n?
   解决方法1.
   用普通查找法,算法复杂度O(n).

const normal_search = (arr,n)=>{
   let i=0;
   while (i<arr.length){
     console.log("普通查找走了一次",i,arr[i],n);
     if(arr[i]===n){
       return i
     }
       i+=1;
   }
   return -1
 };
 console.log("普通查找",arr,normal_search(arr,99));

解决方法2.
用二分查找法,算法复杂度O(log n).

  const binary_search=(arr,n)=>{
    const binary_search_copy=(arr,n,start,end)=>{
      console.log("二分查找走了一次");
      if(arr.length<1){return -1};
      let middle = Math.floor((start+end)/2);
      if(n===arr[middle]){
        return middle
      }else if(n<=arr[middle]){
        return binary_search_copy(arr,n,start,middle-1)
      }else if(n>arr[middle]){
        return binary_search_copy(arr,n,middle+1,end)
      }
    };
    return  binary_search_copy(arr,n,0,arr.length)
  };
  console.log("二分查找",arr,binary_search(arr,99)); // 6
  console.log("二分查找",arr,binary_search(arr,166)); // 15