namespace IStation
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{
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public class ModeHelper
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{
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/// <summary>
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/// 结构：用于统计每个数出现的次数
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/// </summary>
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struct Stats
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{
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//数字，出现的次数
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public double Number;
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public int Count;
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//构造函数
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public Stats(double n, int c)
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{
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Number = n;
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Count = c;
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}
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}
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/// <summary>
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/// 计算数组的众数
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/// </summary>
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/// <param name="array">数组</param>
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/// <param name="threshold">数量阈值，众数数量若多于次数则认为没有众数</param>
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/// <returns></returns>
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public static double[] ModeOf(double[] array, int threshold = 5)
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{
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//数组排序-统计各元素数量-按各元素数量排序-再统计最多的元素
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//1.输入合法性检验
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if (array == null || array.Length == 0 || threshold < 1)
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{
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return new double[] { };
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}
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//2.制作数组副本，后面的操作将不修改数组本身
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double[] tempArray = new double[array.Length];
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array.CopyTo(tempArray, 0);
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//3.数组排序
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double temp;
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for (int i = 0; i < tempArray.Length; i++)
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{
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for (int j = i; j < tempArray.Length; j++)
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{
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if (tempArray[i] < tempArray[j])
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{
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temp = tempArray[i];
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tempArray[i] = tempArray[j];
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tempArray[j] = temp;
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}
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}
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}
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//4.统计不同的元素数
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int counter = 1;
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for (int i = 1; i < tempArray.Length; i++)
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{
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if (tempArray[i] != tempArray[i - 1])
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{
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counter++;
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}
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}
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//5.统计各个元素数量
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int flag = 0;
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Stats[] statsArray = new Stats[counter];
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statsArray[flag].Number = tempArray[0];
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statsArray[flag].Count = 1;
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for (int i = 1; i < tempArray.Length; i++)
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{
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if (tempArray[i] == statsArray[flag].Number)
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{
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statsArray[flag].Count++;
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}
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else
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{
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flag++;
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statsArray[flag].Number = tempArray[i];
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statsArray[flag].Count = 1;
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}
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}
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//6.按元素在原数组内数量（Count属性）降序排列
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// 数量相等的元素则按大小升序排列
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for (int i = 0; i < statsArray.Length; i++)
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{
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for (int j = i; j < statsArray.Length; j++)
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{
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if (statsArray[i].Count < statsArray[j].Count ||
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(statsArray[i].Count == statsArray[j].Count &&
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statsArray[i].Number > statsArray[j].Number))
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{
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temp = statsArray[i].Number;
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statsArray[i].Number = statsArray[j].Number;
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statsArray[j].Number = temp;
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temp = statsArray[i].Count;
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statsArray[i].Count = statsArray[j].Count;
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statsArray[j].Count = (int)temp;
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}
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}
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}
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//7.统计众数数量
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int count = 1;
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if (statsArray.Length > threshold &&
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statsArray[threshold].Count == statsArray[0].Count)
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{
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//众数多余阈值数量，则认为没有众数
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return new double[] { };
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}
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else
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{
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for (int i = 1; i < statsArray.Length && i < threshold; i++)
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{
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if (statsArray[i].Count == statsArray[i - 1].Count)
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{
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count++;
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}
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else break;
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}
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}
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//8.生成返回众数数组
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double[] result = new double[count];
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for (int i = 0; i < count; i++)
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{
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result[i] = statsArray[i].Number;
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}
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return result;
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}
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}
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}
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