C # permutation and combination algorithms

// Sort and combine public class fullarrange {// <summary> /// sort and combine /// </Summary> /// <Param name = "str"> string </ param> // <Param name = "splitstr"> delimiter, for example, ";" </param> // <returns> </returns> Public static list <string> getarrangeresult (string STR, string splitstr) {STR = Str. trim (); If (string. isnullorempty (STR) {return new list <string> ();} else if (Str. length = 1) {return new list <string> {STR };} else if (Str. length = 2) {string [] CA = Str. split (New char [] {convert. tochar (splitstr)}); return new list <string> () {Ca [0]. tostring () + splitstr + Ca [1]. tostring (), Ca [1]. tostring () + splitstr + Ca [0]. tostring () };} else {string [] array = Str. split (New char [] {convert. tochar (splitstr)}); List <string> splittemp = new list <string> (); List <string> temp = getarrangestring (array [0]. tostring (), array [1]. tostring (); For (INT I = 2; I <array. length; I ++) {int COUNT = temp. count; For (Int J = 0; j <count; j ++) {temp. addrange (getarrangestring (temp [J], array [I]); temp. remove (temp [J]); j --; count -- ;}} foreach (VAR item in temp) {var mstr = ""; foreach (VAR s in item) {mstr + = S. tostring () + ";";} splittemp. add (mstr. trimend (';');} return splittemp;} public static list <string> getarrangestring (string parent, string child) {list <string> temp = new list <string> (); For (INT I = 0; I <= parent. length; I ++) {temp. add (parent. insert (I, child. tostring ();} return temp ;}}