算法练习-- C# DFS 全排列算法

来源：互联网发布：init 1 ubuntu 编辑：程序博客网时间：2024/05/16 05:27
void Main(){var r = A(new List<string>(){"a","b","c","d","e","f"});Console.WriteLine(r.Count);Console.WriteLine(r);}//1. loop each element//2. take out first,2nd... element //3. if after_take_out.Length > 1 then recursive//4. get child result then combine into new resultstatic List<string> A(List<string> arr){if(arr.Count <= 1){return arr;}if(arr.Count == 2){return new List<string>(){arr[0]+","+arr[1],arr[1]+","+arr[0]};}var ret = new List<string>();for(var i = 0;i < arr.Count;i ++){var tmp = new List<string>(arr);var takeOut = arr[i];arr.RemoveAt(i);if(arr.Count > 1){var childR = A(arr);var r = GetResult(takeOut, childR);ret.AddRange(r);}}return ret;}//e.g GetResult("a",["b,c","c,b"])//[a,b,c]//[b,a,c]//[b,c,a]//[a,c,b]//[c,a,b]//[c,b,a]static List<string> GetResult(string val, List<string> oldResult){var ret = new List<string>();for(var i = 0;i < oldResult.Count; i++){var r = GetResult(val, oldResult[i]);foreach(var str in r){ret.Add(str);}}return ret;}//e.g. GetResult("a", "b,c,d")//[a,b,c,d]//[b,a,c,d]//[b,c,a,d]//[b,c,d,a]static List<string> GetResult(string val, string old){var newRet = new List<string>();var arr = old.Split(',');for(var i = 0;i <= arr.Length ; i++){var tmp = new List<string>(arr);tmp.Insert(i,val);newRet.Add(string.Join(",",tmp));}return newRet;}
0 0