/// <summary>
/// * 二分查找算法:
/// * 要求:有序,线性结构
/// * 时间复杂度O[log(n)]
/// * 循环实现
/// * middle = (low + high) / 2;
/// </summary>
/// <param name="arr"></param>
/// <param name="des"></param>
/// <returns></returns>
public int Binary_Search(IpRecord[] arr, long key, out SearchRecord recorder)
{
recorder = new SearchRecord();
int search_count = 0;
int low = 0;
int high = arr.Length - 1;
while (low <= high)
{
++search_count;
int middle = (low + high) / 2;
//先拿中间的值与查找的值比较,大于中间的值,说明查找的值索引在[low,middle)
recorder.Progress.Add(SearchRecord.FormatProgress(middle, middle));
if (arr[middle].CompareTo(key) == 0)
{
recorder.IpRecord = arr[middle];
recorder.Count = search_count;
recorder.Index = middle;
return(middle);
}
else if (arr[middle].CompareTo(key) > 0) // > key
{
high = middle - 1;
recorder.Progress.Add("*" + SearchRecord.FormatProgress(low, high));
}
else
{
low = middle + 1;
recorder.Progress.Add("*" + SearchRecord.FormatProgress(low, high));
}
}
recorder.Index = -1;
return(-1);
}
/// <summary>
/// * 斐波那契 查找:
/// * 要求:有序,线性结构
/// * 时间复杂度O[log(n)]
/// * middle = low + Fib[k - 1] - 1;
///
/// 修改部分：
/// 传入数组之后不创建临时数组， 根据数组长度在斐波那契数组中index值，
/// 判断 if (mid >= arr.Length) {
/// high = mid - 1; fibIndex = fibIndex - 1;
/// } else {
/// // 原来判断方法
/// }
/// </summary>
/// <param name="arr">需要查找的原数组</param>
/// <param name="key">查找的元素</param>
/// <param name="recorder"></param>
/// <param name="fibIndex">数组长度在斐波那契数组中index值， 如果不提供， 会自动计算</param>
/// <returns></returns>
public int Fibonacci_Search_Improved(IpRecord[] arr, long key, out SearchRecord recorder, int fibIndex = -1)
{
recorder = new SearchRecord();
int search_count = 0;
int low = 0;
int high = arr.Length - 1;
int mid = 0;
//斐波那契分割数值下标
if (fibIndex < 0)
{
int k = 0;
//获取斐波那契分割数值下标
while (arr.Length > Fib[k] - 1)
{
k++;
}
fibIndex = k;
}
while (low <= high)
{
++search_count;
// low：起始位置
// 前半部分有f[k-1]个元素，由于下标从0开始
// 则-1 获取 黄金分割位置元素的下标
mid = low + Fib[fibIndex - 1] - 1;
recorder.Progress.Add(SearchRecord.FormatProgress(mid, mid));
if (mid >= arr.Length)
{
// 如果超出数组长度， 选哟查找的元素肯定在分割点左侧
// 这样判断就不需要新建和补齐临时数组了
high = mid - 1;
fibIndex = fibIndex - 1;
recorder.Progress.Add(SearchRecord.FormatProgress(low, high));
}
else
{
if (arr[mid].CompareTo(key) > 0) // > key
{
// 查找前半部分，高位指针移动
high = mid - 1;
// （全部元素） = （前半部分）+（后半部分）
// f[k] = f[k-1] + f[k-1]
// 因为前半部分有f[k-1]个元素，所以 k = k-1
fibIndex = fibIndex - 1;
recorder.Progress.Add(SearchRecord.FormatProgress(low, high));
}
else if (arr[mid].CompareTo(key) < 0) // arr[mid] < key
{
// 查找后半部分，高位指针移动
low = mid + 1;
// （全部元素） = （前半部分）+（后半部分）
// f[k] = f[k-1] + f[k-1]
// 因为后半部分有f[k-2]个元素，所以 k = k-2
fibIndex = fibIndex - 2;
recorder.Progress.Add(SearchRecord.FormatProgress(low, high));
}
else
{
recorder.IpRecord = arr[mid];
recorder.Count = search_count;
recorder.Index = mid;
return(mid);
}
}
}
recorder.Index = -1;
return(-1);
}
