边看边写（排列组合及丑数问题 ）
来源：互联网 发布：sql循环语句 update 编辑：程序博客网 时间：2024/05/18 22:15
#region 字符串排列 /// <summary> /// 输入字符串，打印该字符串的所有排列 /// </summary> class ListOperator<T> where T:IComparable<T> { private List<T> str; public ListOperator() { if (str == null) str = new List<T>(); } public ListOperator(List<T> list) { if (str == null) str = new List<T>(); str = list; } /// <summary> /// 排列 /// </summary> /// <param name="m"></param> public void Permutation() { Console.WriteLine(); if (str == null || str.Count == 0) return; Permutation(str,0); Console.WriteLine(); } public void Permutation(List<T> pStr,int begin) { if (begin == str.Count) { pStr.ForEach(l => Console.Write(l)); Console.Write(" , "); } else { for (int pCh = begin; pCh != pStr.Count; pCh++) { T temp = pStr[pCh]; pStr[pCh] = pStr[begin]; pStr[begin] = temp; Permutation(pStr, begin + 1); temp = pStr[pCh]; pStr[pCh] = pStr[begin]; pStr[begin] = temp; } } } /// <summary> /// 组合 /// </summary> /// <param name="m"></param> public void Combine(int m) { if (str.Count < m) return; List<T> result =new List<T>(); Combine(str,ref result,m); } public void Combine(List<T> pStr,ref List<T> result, int m) { if (m == 0) { result.ForEach(r => Console.Write(r)); Console.Write(","); //result.Add(default(T)); } else { if (pStr.Count == 0) return; result.Add(pStr[0]); Combine(pStr.GetRange(1, pStr.Count - 1), ref result, m - 1); result.RemoveAt(result.Count - 1); Combine(pStr.GetRange(1, pStr.Count - 1), ref result, m); } } /// <summary> /// 数组中出现次数超过一半的数字 /// </summary> /// <param name="m"></param> #region 方法一，此方法修改了数组 public T MoreThanHalfByPartion() { if (str == null || str.Count == 0) return default(T); int middle = str.Count >> 1; int start = 0; int end = str.Count - 1; int index = Partition(str, start, end); while (index != middle) { if (index < middle) { start = index + 1; index = Partition(str, start, end); } else { end = index - 1; index = Partition(str, start,end ); } } if (!CheckMoreThanHalf(str[index])) Console.WriteLine(str[index] + "的结果并没有超过一半！"); return str[index]; } public int Partition(List<T> num,int start,int end) { T pivotkey = num[start]; while (start < end) { while (num[end].CompareTo(pivotkey)>=0 && start < end) end--; T temp = num[start]; num[start] = num[end]; num[end] = temp; while (num[start].CompareTo(pivotkey) <= 0 && start < end) start++; temp = num[start]; num[start] = num[end]; num[end] = temp; } return start; } #endregion #region 方法二，此方法没有修改了数组 public T MoreThanHalfByFeature() { if(str==null || str.Count==0) return default(T); T result = default(T); int times = 0; str.ForEach( delegate (T num) { if (times == 0) { result = num; times = 1; } else if (num.CompareTo(result) == 0) { times++; } else times--; } ); if (!CheckMoreThanHalf(result)) Console.WriteLine(result+"的结果并没有超过一半！"); return result; } public bool CheckMoreThanHalf(T result) { int times = 0; str.ForEach( delegate(T num) { if (num.CompareTo(result) == 0) times++; }); if (times * 2 <= str.Count) return false; return true; } #endregion #region 丑数问题 /// <summary> /// 我们把只包含因子2、3、5的数称作丑数(ugly number)。求按从小到大的第1500个丑数。例如 /// 6,8是丑数，14不是，因为它包含因子7.习惯是我们把1作为第一个丑数。 /// </summary> public int GetUglyNumber(int index) { System.DateTime startTime = System.DateTime.Now; if(index<=0) return 0; List<int> pUglyNumber = new List<int>() { 1 }; int pMultiply2 = 0; int pMultiply3 = 0; int pMultiply5 = 0; int nextUglyIndex =1; while (nextUglyIndex < index) { int min = Min(pUglyNumber[pMultiply2]*2,pUglyNumber[pMultiply3]*3,pUglyNumber[pMultiply5]*5); pUglyNumber.Add(min); while (pUglyNumber[pMultiply2] * 2 <= pUglyNumber[nextUglyIndex]) pMultiply2++; while (pUglyNumber[pMultiply3] * 3 <= pUglyNumber[nextUglyIndex]) pMultiply3++; while (pUglyNumber[pMultiply5] * 5 <= pUglyNumber[nextUglyIndex]) pMultiply5++; nextUglyIndex++; } System.DateTime endTime = System.DateTime.Now; TimeSpan span = endTime.Subtract(startTime); Console.WriteLine("计算时间："+span.TotalMilliseconds); return pUglyNumber.Last(); } public int Min(int number1, int number2, int number3) { int min = number1 < number2 ? number1 : number2; min = number3 < min ? number3 : min; return min; } #endregion void Check() { try { if (str == null) throw new Exception("str不存在！"); else if (str.Count == 0) throw new Exception("str没有元素！"); else throw new Exception("未知错误！"); } catch(Exception ex) { Console.WriteLine(ex.Message); } } } #endregion
