//二分查找
class  SecondFind
{
    public static void main(String[] args) 
    {
        //定义数组
        int [] data=new int[]{2,3,4,5,6,7,8,9};
        int index=getIndex(data,77);
        System.out.print("index="+index);
    }
    public static int getIndex(int []arr,int num){
        int min=0,max=arr.length-1;
        int mid=(min+max)/2;
        while(arr[max]>=arr[min]){
            mid=(min+max)/2;
            if(num>arr[mid])
                min=mid+1;
            else if (num<arr[mid])
                max=mid-1;
            else 
                return mid;
            }
            return -1;
                 }
        
}