这个算法，相信大家都懂，但是不真正的手动写一遍，总觉得不得劲。这不，手动写一遍就是有不一样的效果出现了。
往左折半，还是往右走比较简单，其实这两个算法最关键的是：退出条件 min > max 和下次折半时下标或上标位置要+1或-1
C#
/// <summary>
/// 递归的纯算法实现
/// </summary>
/// <param name="arrList"></param>
/// <param name="min"></param>
/// <param name="max"></param>
/// <param name="des"></param>
/// <returns>命中目标的索引</returns>
public int RecursionSearch(int[] arrList, int min, int max, int des)
{
if (min > max) return -1;
var midIndex = (min + max) / 2;
var midValue = arrList[midIndex];
if (midValue == des) return midIndex;
return midValue < des ? RecursionSearch(arrList, midIndex + 1, max, des) : RecursionSearch(arrList, min, midIndex - 1, des);
}
/// <summary>
/// 普通算法纯算法实现
/// </summary>
/// <param name="arrList"></param>
/// <param name="des"></param>
/// <returns></returns>
public int CommonSearch(int[] arrList, int des)
{
var min = 0;
var max = arrList.Length - 1;
while (min < max)
{
var mid = (max + min) / 2;
var midValue = arrList[mid];
if (midValue == des) return mid;
if (midValue < des) min = mid + 1; //向右搜索
if (midValue > des) max = mid - 1; //向左搜索
}
return -1;
}