C# 排列组合类源码 以及调用示例

// 调用方法如下：
//
// 1.GetPermutation(T[], startIndex, endIndex)
// 对startIndex到endIndex进行排列，其余元素不变
//
// 2.GetPermutation(T[])
// 返回数组所有元素的全排列
//
// 3.GetPermutation(T[], n)
// 返回数组中n个元素的排列
//
// 4.GetCombination(T[], n)
// 返回数组中n个元素的组合

//-----------------------------------------------------------------------------//// 算法：排列组合类////// 调用方法如下：//// 1.GetPermutation(T[], startIndex, endIndex)// 对startIndex到endIndex进行排列，其余元素不变//// 2.GetPermutation(T[])// 返回数组所有元素的全排列//// 3.GetPermutation(T[], n)// 返回数组中n个元素的排列//// 4.GetCombination(T[], n)// 返回数组中n个元素的组合//// 版本历史：// V0.1 2010-01-20 摘要：首次创建 ////-----------------------------------------------------------------------------using System;using System.Collections.Generic;namespace Arithmetic{public class PermutationAndCombination<T>{#region 内部方法/// <summary>/// 递归算法求数组的组合(私有成员)/// </summary>/// <param name="list">返回的范型</param>/// <param name="t">所求数组</param>/// <param name="n">辅助变量</param>/// <param name="m">辅助变量</param>/// <param name="b">辅助数组</param>/// <param name="M">辅助变量M</param>private static void GetCombination(ref List<T[]> list, T[] t, int n, int m, int[] b, int M){for (int i = n; i >= m; i--){b[m - 1] = i - 1;if (m > 1){GetCombination(ref list, t, i - 1, m - 1, b, M);}else{if (list == null){list = new List<T[]>();}T[] temp = new T[M];for (int j = 0; j < b.Length; j ){temp[j] = t[b[j]];}list.Add(temp);}}}/// <summary>/// 递归算法求排列(私有成员)/// </summary>/// <param name="list">返回的列表</param>/// <param name="t">所求数组</param>/// <param name="startIndex">起始标号</param>/// <param name="endIndex">结束标号</param>private static void GetPermutation(ref List<T[]> list, T[] t, int startIndex, int endIndex){if (startIndex == endIndex){if (list == null){list = new List<T[]>();}T[] temp = new T[t.Length];t.CopyTo(temp, 0);list.Add(temp);}else{for (int i = startIndex; i <= endIndex; i ){Swap(ref t[startIndex], ref t[i]);GetPermutation(ref list, t, startIndex 1, endIndex);Swap(ref t[startIndex], ref t[i]);}}}#endregion#region 公共方法/// <summary>/// 交换两个变量/// </summary>/// <param name="a">变量1</param>/// <param name="b">变量2</param>public static void Swap(ref T a, ref T b){T temp = a;a = b;b = temp;}/// <summary>/// 求从起始标号到结束标号的排列，其余元素不变/// </summary>/// <param name="t">所求数组</param>/// <param name="startIndex">起始标号</param>/// <param name="endIndex">结束标号</param>/// <returns>从起始标号到结束标号排列的范型</returns>public static List<T[]> GetPermutation(T[] t, int startIndex, int endIndex){if (startIndex < 0 || endIndex > t.Length - 1){return null;}List<T[]> list = new List<T[]>();GetPermutation(ref list, t, startIndex, endIndex);return list;}/// <summary>/// 返回数组所有元素的全排列/// </summary>/// <param name="t">所求数组</param>/// <returns>全排列的范型</returns>public static List<T[]> GetPermutation(T[] t){return GetPermutation(t, 0, t.Length - 1);}/// <summary>/// 求数组中n个元素的排列/// </summary>/// <param name="t">所求数组</param>/// <param name="n">元素个数</param>/// <returns>数组中n个元素的排列</returns>public static List<T[]> GetPermutation(T[] t, int n){if (n > t.Length){return null;}List<T[]> list = new List<T[]>();List<T[]> c = GetCombination(t, n);for (int i = 0; i < c.Count; i ){List<T[]> l = new List<T[]>();GetPermutation(ref l, c[i], 0, n - 1);list.AddRange(l);}return list;}/// <summary>/// 求数组中n个元素的组合/// </summary>/// <param name="t">所求数组</param>/// <param name="n">元素个数</param>/// <returns>数组中n个元素的组合的范型</returns>public static List<T[]> GetCombination(T[] t, int n){if (t.Length < n){return null;}int[] temp = new int[n];List<T[]> list = new List<T[]>();GetCombination(ref list, t, t.Length, n, temp, n);return list;}#endregion}}