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Given a collection of distinct numbers, return all possible permutations.
For example,[1,2,3] have the following permutations:
[ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ]
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1 public class Solution { 2 public List<List<Integer>> permute(int[] nums) { 3 List<List<Integer>> ans = new ArrayList<List<Integer>>(); 4 DFS(ans,0,nums); 5 return ans; 6 } 7 8 public void DFS(List<List<Integer>> ans, int k, int[] nums){ 9 if(k == nums.length){ 10 List<Integer> list = new ArrayList<Integer>(); 11 for(int n : nums) list.add(n); 12 ans.add(list); 13 } 14 15 for(int i = k; i< nums.length; i++){ 16 Swap(nums,k,i); 17 DFS(ans,k+1,nums); 18 Swap(nums,k,i); 19 } 20 } 21 22 public void Swap(int[] num, int i, int j){ 23 int tmp = num[i]; 24 num[i] = num[j]; 25 num[j] = tmp; 26 } 27 }
全排列就是从第一个数字起每个数分别与它后面的数字交换.
大神链接：
http://blog.csdn.net/happyaaaaaaaaaaa/article/details/51534048
46. Permutations java solutions
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原文地址：http://www.cnblogs.com/guoguolan/p/5619346.html
