二分法查找方法
public static int binarySearch(int[] arr,int start,int end,int target)
{
//二分查找的前提是数组有序
Arrays.sort(arr);
int mid=(start+end)>>1;
if(start<=end)
{
if(arr[mid]==target)
{
return mid;
}
else if(arr[mid]<target)
{
start=mid+1;
return binarySearch(arr,start,end,target);
}
else
{
end=mid-1;
return binarySearch(arr,start,end,target);
}
}
return -1;
}