133 lines
4.0 KiB
C#
133 lines
4.0 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Numerics;
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using UnityEngine;
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namespace XGame
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{
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/// <summary>
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/// ALgorithm相关的实用函数。
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/// </summary>
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public static partial class Utility
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{
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public static void Swap<T>(ref T x, ref T y)
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{
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T t = x;
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x = y;
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y = t;
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}
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/// <summary>
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/// 递归求组合（从n个不同元素中取出m个元素组合）
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="list">结果列表</param>
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/// <param name="arr">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="pos">辅助下标存储数组</param>
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/// <param name="M">辅助变量</param>
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public static void GetCombination<T>(ref List<T[]> list, T[] arr, int n, int m, int[] pos, 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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pos[m - 1] = i - 1;
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if (m > 1)
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{
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GetCombination(ref list, arr, i - 1, m - 1, pos, M);
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}
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else
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{
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T[] temp = new T[M];
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for (int j = 0; j < M; j++)
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{
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temp[j] = arr[pos[j]];
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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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list.Add(temp);
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}
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}
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}
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/// <summary>
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/// 数组中n个元素的组合
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="arr">所求数组</param>
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/// <param name="n">元素个数</param>
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/// <returns>组合结果列表</returns>
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public static List<T[]> GetCombination<T>(T[] arr, int n)
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{
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if (arr.Length < n)
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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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GetCombination(ref list, arr, arr.Length, n, new int[n], n);
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return list;
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}
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/// <summary>
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/// 递归求排列（从n个不同元素中取出m个元素排列）
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="result">结果列表</param>
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/// <param name="list">所求数组</param>
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/// <param name="start">起始标号</param>
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/// <param name="end">结束标号</param>
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public static void GetPermutation<T>(ref List<T[]> list, T[] arr, int start, int end)
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{
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if (start == end)
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{
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T[] temp = new T[arr.Length];
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arr.CopyTo(temp, 0);
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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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list.Add(temp);
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}
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for (int i = start; i <= end; i++)
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{
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Swap(ref arr[i], ref arr[start]);
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GetPermutation(ref list, arr, start + 1, end);
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Swap(ref arr[i], ref arr[start]);
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}
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}
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/// <summary>
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/// 数组n个元素的排列
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="arr">所求数组</param>
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/// <param name="n">元素个数</param>
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/// <returns>排列结果列表</returns>
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public static List<T[]> GetPermutation<T>(T[] arr, int n)
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{
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if (arr.Length < n)
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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[]> comList = GetCombination(arr, n);
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foreach (var com in comList)
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{
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List<T[]> perList = new List<T[]>();
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GetPermutation(ref perList, com, 0, n - 1);
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list.AddRange(perList);
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}
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return list;
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}
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}
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}
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