namespace PBS.WinFrmUI.Hydro
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{
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// 算法:排列组合类
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//
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// 版权所有(C) Snowdust
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// 个人博客 http://blog.csdn.net/snowdust & http://snowdust.cnblogs.com
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// MSN & Email snowdust77@sina.com
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//
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// 此源代码可免费用于各类软件（含商业软件）
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// 允许对此代码的进一步修改与开发
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// 但必须完整保留此版权信息
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//
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// 调用方法如下:
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//
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// 1.GetPermutation(T[], startIndex, endIndex)
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// 对startIndex到endIndex进行排列，其余元素不变
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//
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// 2.GetPermutation(T[])
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// 返回数组所有元素的全排列
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//
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// 3.GetPermutation(T[], n)
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// 返回数组中n个元素的排列
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//
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// 4.GetCombination(T[], n)
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// 返回数组中n个元素的组合
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//使用实例
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//int[] arr = new int[6];
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//for (int i = 0; i < arr.Length; i++)
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//{
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// arr[i] = i + 1;
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//}
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////求排列
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//List<int[]> lst_Permutation = Eventech.Model.PermutationAndCombination<int>.GetPermutation(arr, 3);
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////求组合
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//List<int[]> lst_Combination = Eventech.Model.PermutationAndCombination<int>.GetCombination(arr, 3);
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public class PermutationAndCombination<T>
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{
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/// <summary>
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/// 交换两个变量
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/// </summary>
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/// <param name="a">变量1</param>
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/// <param name="b">变量2</param>
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public static void Swap(ref T a, ref T b)
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{
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T temp = a;
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a = b;
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b = temp;
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}
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/// <summary>
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/// 递归算法求数组的组合(私有成员)
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/// </summary>
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/// <param name="list">返回的范型</param>
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/// <param name="t">所求数组</param>
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/// <param name="n">辅助变量</param>
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/// <param name="m">辅助变量</param>
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/// <param name="b">辅助数组</param>
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/// <param name="M">辅助变量M</param>
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private static void GetCombination(ref List<T[]> list, T[] t, int n, int m, int[] b, int M)
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{
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for (int i = n; i >= m; i--)
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{
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b[m - 1] = i - 1;
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if (m > 1)
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{
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GetCombination(ref list, t, i - 1, m - 1, b, M);
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}
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else
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{
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if (list == null)
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{
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list = new List<T[]>();
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}
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T[] temp = new T[M];
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for (int j = 0; j < b.Length; j++)
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{
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temp[j] = t[b[j]];
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}
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list.Add(temp);
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}
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}
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}
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/// <summary>
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/// 递归算法求排列(私有成员)
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/// </summary>
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/// <param name="list">返回的列表</param>
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/// <param name="t">所求数组</param>
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/// <param name="startIndex">起始标号</param>
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/// <param name="endIndex">结束标号</param>
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private static void GetPermutation(ref List<T[]> list, T[] t, int startIndex, int endIndex)
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{
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if (startIndex == endIndex)
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{
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if (list == null)
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{
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list = new List<T[]>();
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}
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T[] temp = new T[t.Length];
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t.CopyTo(temp, 0);
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list.Add(temp);
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}
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else
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{
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for (int i = startIndex; i <= endIndex; i++)
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{
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Swap(ref t[startIndex], ref t[i]);
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GetPermutation(ref list, t, startIndex + 1, endIndex);
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Swap(ref t[startIndex], ref t[i]);
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}
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}
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}
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/// <summary>
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/// 求从起始标号到结束标号的排列，其余元素不变
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/// </summary>
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/// <param name="t">所求数组</param>
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/// <param name="startIndex">起始标号</param>
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/// <param name="endIndex">结束标号</param>
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/// <returns>从起始标号到结束标号排列的范型</returns>
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public static List<T[]> GetPermutation(T[] t, int startIndex, int endIndex)
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{
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if (startIndex < 0 || endIndex > t.Length - 1)
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{
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return null;
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}
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List<T[]> list = new List<T[]>();
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GetPermutation(ref list, t, startIndex, endIndex);
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return list;
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}
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/// <summary>
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/// 返回数组所有元素的全排列
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/// </summary>
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/// <param name="t">所求数组</param>
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/// <returns>全排列的范型</returns>
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public static List<T[]> GetPermutation(T[] t)
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{
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return GetPermutation(t, 0, t.Length - 1);
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}
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/// <summary>
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/// 求数组中n个元素的排列
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/// </summary>
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/// <param name="t">所求数组</param>
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/// <param name="n">元素个数</param>
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/// <returns>数组中n个元素的排列</returns>
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public static List<T[]> GetPermutation(T[] t, int n)
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{
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if (n > t.Length)
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{
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return null;
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}
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List<T[]> list = new List<T[]>();
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List<T[]> c = GetCombination(t, n);
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for (int i = 0; i < c.Count; i++)
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{
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List<T[]> l = new List<T[]>();
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GetPermutation(ref l, c[i], 0, n - 1);
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list.AddRange(l);
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}
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return list;
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}
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/// <summary>
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/// 求数组中n个元素的组合
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/// </summary>
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/// <param name="t">所求数组</param>
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/// <param name="n">元素个数</param>
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/// <returns>数组中n个元素的组合的范型</returns>
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public static List<T[]> GetCombination(T[] t, int n)
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{
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if (t.Length < n)
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{
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return null;
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}
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int[] temp = new int[n];
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List<T[]> list = new List<T[]>();
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GetCombination(ref list, t, t.Length, n, temp, n);
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return list;
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}
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}
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}
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