LeetCode 47. 全排列 II

雨点打透心脏的1/2处 2022-11-03 15:30 140阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODE5OTc3MA_size_16_color_FFFFFF_t_70]  
[官方][Link 1]

class Solution {
        
        boolean[] vis;
        public List<List<Integer>> permuteUnique(int[] nums) {
        
            List<List<Integer>> ans = new ArrayList<List<Integer>>();
            List<Integer> perm = new ArrayList<Integer>();
            vis = new boolean[nums.length];
            Arrays.sort(nums);
            backtrack(nums, ans, 0, perm);
            return ans;
        }
    
        public void backtrack(int[] nums, List<List<Integer>> ans, int idx, List<Integer> perm){
        
            if(idx == nums.length){
        
                ans.add(new ArrayList<Integer>(perm));
                return;
            }
            for(int i = 0; i < nums.length; i++){
        
                if(vis[i] || (i > 0 && nums[i] == nums[i - 1] && !vis[i - 1])){
        
                    continue;
                }
                perm.add(nums[i]);
                vis[i] = true;
                backtrack(nums, ans, idx + 1, perm);
                vis[i] = false;
                perm.remove(idx);
            }
        }
    }

//写法二：用set剪纸
    class Solution {
        
        boolean[] vis;
        public List<List<Integer>> permuteUnique(int[] nums) {
        
            List<List<Integer>> ans = new ArrayList<List<Integer>>();
            List<Integer> perm = new ArrayList<Integer>();
            vis = new boolean[nums.length];
            Arrays.sort(nums);
            backtrack(nums, ans, 0);
            return ans;
        }
    
        public void backtrack(int[] nums, List<List<Integer>> ans, int idx){
        
            if(idx == nums.length){
        
                ans.add(Arrays.stream(nums).boxed().collect(Collectors.toList()));
                return;
            }
            HashSet<Integer> set = new HashSet<Integer>();
            for(int i = idx; i < nums.length; i++){
        
                if(set.contains(nums[i]))
                    continue;
                set.add(nums[i]);
                swap(nums, i, idx);
                backtrack(nums, ans, idx + 1);
                swap(nums, i, idx);
            }
        }
    
        private void swap(int[] nums, int i, int j){
        
            int tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODE5OTc3MA_size_16_color_FFFFFF_t_70]: /images/20221023/e5401c26ba514ae49ec77ba1e923e05e.png
[Link 1]: https://leetcode-cn.com/problems/permutations-ii/solution/quan-pai-lie-ii-by-leetcode-solution/