Study Notes: arrange and combine

Use string [] arr = {"qi", "ji", "ta"}; // sort the List <string []> lst_Permutation = PermutationAndCombination <string>. getPermutation (arr, 2); // returns the combined List <string []> lst_Combination = PermutationAndCombination <string>. getCombination (arr, 2); Code

Using System; using System. collections. generic; using System. linq; using System. text; using System. threading. tasks; namespace ConsoleApplication1 {public class PermutationAndCombination <T> {// <summary> // exchange two variables /// </summary> // <param name = "a"> variable 1 </param> /// <param name = "B"> variable 2 </param> public static void Swap (ref T, ref T B) {T temp = a; a = B; B = temp;} // <summary> // recursive algorithm to find the combination of arrays (Private Members) /// </summary> /// <param name = "list"> returned Model </param> /// <param name = "t"> array </ param> /// <param name = "n"> auxiliary variable </param> /// <param name = "m"> auxiliary variable </param> // <param name = "B"> secondary array </param> // <param name = "M"> secondary variable 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> // recursive algorithm for sorting (Private member) /// </summary> /// <param name = "list"> returned list </param> /// <param name = "t"> array </param> /// <param name = "startIndex"> start label </param> /// <param name = "endIndex"> end label </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]) ;}} /// <summary> /// sort the start and end labels, other elements remain unchanged /// </summary> /// <param name = "t"> array </param> /// <param name = "startIndex"> Start number </param> /// <param name = "endIndex"> end label </param> /// <returns> type from start label to end label </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> /// return the full arrangement of all elements in the array /// </summary> /// <param name = "t"> array </param> /// <returns> fully-arranged paradigm </returns> public static List <T []> GetPermutation (T [] t) {return GetPermutation (t, 0, t. length-1 );} /// <summary> /// sort the n elements in the array /// </summary> /// <param name = "t"> array </param> /// <param name = "n"> Number of elements </param> /// arrange n elements in the <returns> array </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> /// evaluate the combination of n elements in the array /// </summary> /// <param name = "t"> obtain the array </param> /// <param name = "n"> Number of elements </param> /// the combination of n elements in the <returns> array. </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 ;}}}