My algorithm Learning (1) ---- full array Arrangement

Seeing the beautiful and practical code written by others, I finally made up my mind to study algorithms and record my learning achievements here.

Two days ago, I saw the full array arrangement, so I realized it according to other people's ideas. I felt like I understood it. I was a little happy. I recorded it.

/** Full array arrangement */public class myAllSort {public static void sort (int [] number, int start, int end) {int temp; // if the elements in the array are lost to the last one, the output proves that the elements have met the requirements. if (start = end) {print (number );} // In turn, the first element of the array and the subsequent element are called one by one, and then recursively after the first pair, // the second element of the array and its subsequent elements are called, last run/** 1 2 3 4 --> 1 2 3 4 --> 1 2 3 4*1 4 3 3 3 2 4 --> 1 3 2 4 4*1 3 4 2*1 4 3 2 --> 1 4 3 2*1 4 2 3*2 1 3 4*3 2 1 4*4 2 3 1 **/for (int I = start; I <end; I ++) {temp = number [start]; number [start] = number [I]; number [I] = temp; sort (number, start + 1, end); // print (number); // output the entire sorting process // the original order of the array after the pair is dropped, so that the next time temp = number [start]; number [start] = number [I]; number [I] = temp; //} public static void print (int [] number) {for (int I = 0; I <number. length; I ++) {System. out. print (number [I] + "--");} System. out. println ();} public static void main (String [] args) {int [] number = {1, 2, 4}; sort (number, 0, number. length );}}

There is also an array selection and sorting method. I feel this idea is very useful to me, and I forgot the specific source.

Import java. util. arrayList; import java. util. arrays; import java. util. list;/** depending on how to select a few numbers for sorting * For example: Five to choose three full sorting * algorithm principle: select a number in the array and store it in the Set first, then select other numbers, **/public class ChooseServalFromNumber {public static final int NUM = 4; public static void main (String [] args) {Object [] obj = new String [] {"1", "2", "3", "4"}; List <Object> list = Arrays. asList (obj); chooseNumberSort (list, new ArrayList <Object> ();} public static void chooseNumberSort (List <Object> list, List <Object> target) {// if the number in the target set reaches the number we need, output // if (target. size () = NUM) // System. out. println (target + "--"); if (target. size () = 4) System. out. println (list + "-->" + target + "-- output"); // else // System. out. println (list + "-->" + target); for (int I = 0; I <list. size (); I ++) {List <Object> newList = new ArrayList <Object> (list); List <Object> newTarget = new ArrayList <Object> (target ); newTarget. add (newList. get (I); newList. remove (I); System. out. println (list + "-->" + target); chooseNumberSort (newList, newTarget) ;}}/* output result: [1, 2, 3, 4] --> [] [2, 3, 4] --> [1] [3, 4] --> [1, 2] [4] --> [1, 2, 3] [] --> [1, 2, 3, 4] -- output [3, 4] --> [1, 2] [3] --> [1, 2, 4] [] --> [1, 2, 4, 3] -- output [2, 3, 4] --> [1] [2, 4] --> [1, 3] [4] --> [1, 3, 2] [] --> [1, 3, 2, 4] -- output [2, 4] --> [1, 3] [2] --> [1, 3, 4] [] --> [1, 3, 4, 2] -- output [2, 3, 4] --> [1] [2, 3] --> [1, 4] [3] --> [1, 4, 2] [] --> [1, 4, 2, 3] -- output [2, 3] --> [1, 4] [2] --> [1, 4, 3] [] --> [1, 4, 3, 2] -- output [1, 2, 3, 4] --> [] [1, 3, 4] --> [2] [3, 4] --> [2, 1] [4] --> [2, 1, 3] [] --> [2, 1, 3, 4] -- output [3, 4] --> [2, 1] [3] --> [2, 1, 4] [] --> [2, 1, 4, 3] -- output [1, 3, 4] --> [2] [1, 4] --> [2, 3] [4] --> [2, 3, 1] [] --> [2, 3, 1, 4] -- output [1, 4] --> [2, 3] [1] --> [2, 3, 4] [] --> [2, 3, 4, 1] -- output [1, 3, 4] --> [2] [1, 3] --> [2, 4] [3] --> [2, 4, 1] [] --> [2, 4, 1, 3] -- output [1, 3] --> [2, 4] [1] --> [2, 4, 3] [] --> [2, 4, 3, 1] -- output [1, 2, 3, 4] --> [] [1, 2, 4] --> [3] [2, 4] --> [3, 1] [4] --> [3, 1, 2] [] --> [3, 1, 2, 4] -- output [2, 4] --> [3, 1] [2] --> [3, 1, 4] [] --> [3, 1, 4, 2] -- output [1, 2, 4] --> [3] [1, 4] --> [3, 2] [4] --> [3, 2, 1] [] --> [3, 2, 1, 4] -- output [1, 4] --> [3, 2] [1] --> [3, 2, 4] [] --> [3, 2, 4, 1] -- output [1, 2, 4] --> [3] [1, 2] --> [3, 4] [2] --> [3, 4, 1] [] --> [3, 4, 1, 2] -- output [1, 2] --> [3, 4] [1] --> [3, 4, 2] [] --> [3, 4, 2, 1] -- output [1, 2, 3, 4] --> [] [1, 2, 3] --> [4] [2, 3] --> [4, 1] [3] --> [4, 1, 2] [] --> [4, 1, 2, 3] -- output [2, 3] --> [4, 1] [2] --> [4, 1, 3] [] --> [4, 1, 3, 2] -- output [1, 2, 3] --> [4] [1, 3] --> [4, 2] [3] --> [4, 2, 1] [] --> [4, 2, 1, 3] -- output [1, 3] --> [4, 2] [1] --> [4, 2, 3] [] --> [4, 2, 3, 1] -- output [1, 2, 3] --> [4] [1, 2] --> [4, 3] [2] --> [4, 3, 1] [] --> [4, 3, 1, 2] -- output [1, 2] --> [4, 3] [1] --> [4, 3, 2] [] --> [4, 3, 2, 1] -- output */