上代码:
//折半查找,也叫二分查找
function binerySearch(arr,num){
var left=0;
var right=arr.length-1;
while(left<=right){
var mid=Math.floor(left+(right-left)/2);
if(arr[mid]<num){
left=mid+1;
}else if(arr[mid]>num){
right=mid-1;
}else{
return mid;
}
}
}
var arr=[2,5,6,8,9];
console.log(binerySearch(arr,9));