46. 全排列
给定一个 没有重复 数字的序列,返回其所有可能的全排列。
示例:
输入: [1,2,3] 输出: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ]
class Solution { public List<List<Integer>> permute(int[] nums) { List<List<Integer>> lists = new ArrayList<>(); if(nums == null || nums.length == 0) return lists; boolean[] visited = new boolean[nums.length]; bt(nums,new ArrayList<>(),lists,visited); return lists; } private void bt(int[] nums,List<Integer> list,List<List<Integer>> lists,boolean[] visited){ if(list.size() == nums.length){ lists.add(new ArrayList<>(list)); return; } for(int j = 0;j < nums.length;j++){ if(!visited[j]){ visited[j] = true; list.add(nums[j]); bt(nums,list,lists,visited); visited[j] = false; list.remove(list.size() - 1); } } } }
给定一个可包含重复数字的序列,返回所有不重复的全排列。
示例:
输入: [1,1,2] 输出: [ [1,1,2], [1,2,1], [2,1,1] ]
class Solution { public List<List<Integer>> permuteUnique(int[] nums) { List<List<Integer>> lists = new ArrayList<>(); if(nums == null || nums.length == 0) return lists; boolean[] visited = new boolean[nums.length]; //需要排序先 Arrays.sort(nums); bt(nums,new ArrayList<>(),lists,visited); return lists; } private void bt(int[] nums,List<Integer> list,List<List<Integer>> lists,boolean[] visited){ if(list.size() == nums.length){ lists.add(new ArrayList<>(list)); return; } for(int j = 0;j < nums.length;j++){ if(visited[j] || (j > 0 && nums[j] == nums[j - 1] && !visited[j - 1])){ continue; } visited[j] = true; list.add(nums[j]); bt(nums,list,lists,visited); visited[j] = false; list.remove(list.size() - 1); } } }
一回生,二回熟