public class Q二分查找递归 {
    //查找有序的从小到大的数组
    //返回下标
    public static int f(int[] arr,int right,int left,int key){
        if(right>left){
            return -1;
        }
        int mid=(right+left)/2;

        if(key<arr[mid]){
            return f(arr,right,mid,key);
        }else if(key>arr[mid]){
            return f(arr,mid+1,left,key);
        }else{
            return mid;
        }

    }
    public static void main(String[] args) {
        int[] nums={1,2,3,4,5,6,7,8,9,10};
        System.out.println(f(nums,0, nums.length-1,7));
    }
}