1~n的全排列--阅文集团2018校招笔试题
题目大意：给定整数n，求出1~n的全排列
示例
输入：n=3
输出：[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]
1 import java.util.Scanner; 2 import java.util.ArrayList; 3 4 public class Main{ 5 private void func(ArrayList<Integer> nArray, ArrayList<ArrayList<Integer>> results, ArrayList<Integer> oneResult) { 6 int nArraySize = nArray.size(); 7 if(nArraySize == 0) { 8 results.add(new ArrayList<Integer>(oneResult)); // 要新建一个类加入到结果集中，不然最终结果集中所有结果都一样（因为是同一个ArrayList） 9 return; 10 } 11 int tmp = 0; 12 for(int i=0; i<nArraySize; i++) { 13 tmp = nArray.get(i); 14 nArray.remove(i); 15 oneResult.add(tmp); 16 func(nArray, results, oneResult); 17 nArray.add(i, tmp); 18 oneResult.remove(oneResult.size()-1); 19 } 20 21 } 22 23 public static void main(String[] args) { 24 Main mainClass = new Main(); 25 Scanner in = new Scanner(System.in); 26 while(in.hasNext()) { 27 String input = in.next(); 28 int n = Integer.parseInt(input.split("=")[1]); 29 ArrayList<Integer> nArray = new ArrayList<Integer>(); 30 for(int i=1; i<=n; i++) { 31 nArray.add(i); 32 } 33 34 ArrayList<ArrayList<Integer>> results = new ArrayList<ArrayList<Integer>>(); 35 mainClass.func(nArray, results, new ArrayList<Integer>()); 36 37 /** 38 * 构造输出格式 39 */ 40 StringBuilder stringBuilder = new StringBuilder(); 41 for(int i=0; i<results.size(); i++) { 42 if(i > 0) { 43 stringBuilder.append(","); 44 } 45 stringBuilder.append("["); 46 for(int j=0; j<results.get(i).size(); j++) { 47 if(j > 0) { 48 stringBuilder.append(","); 49 } 50 stringBuilder.append(results.get(i).get(j)); 51 } 52 stringBuilder.append("]"); 53 } 54 55 System.out.println(stringBuilder.toString()); 56 } 57 in.close(); 58 } 59 }
