// <summary>
// 二分查找
// </summary>
// <param name="arr"></param>
// <param name="low">开始索引 0</param>
// <param name="high">结束索引 </param>
// <param name="key">要查找的对象</param>
// <returns></returns>
/// <summary>
/// 二分查找
/// </summary>
/// <param name="arr"></param>
/// <param name="low">开始索引 0</param>
/// <param name="high">结束索引 </param>
/// <param name="key">要查找的对象</param>
public static int BinarySearch(int[] arr, int low, int high, int key)
{
int mid = (low + high) / 2;
if (low > high)
return -1;