leetcode——47.全排列II

回溯

public List<List<Integer>> permuteUnique(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        boolean[] visited = new boolean[nums.length];
        Arrays.sort(nums);
        backtrack(result,nums,new ArrayList<Integer>(),visited);
        return result;
    }

    private void backtrack(List<List<Integer>> result, int[] nums, ArrayList<Integer> temp, boolean[] visited) {
        if(temp.size() == nums.length){
            result.add(new ArrayList<>(temp));
            return;
        }
        for(int i = 0;i<nums.length;i++){
            if(visited[i]) continue;
            if(i>0 && !visited[i-1] && nums[i] == nums[i-1]) continue;
            visited[i] = true;
            temp.add(nums[i]);
            backtrack(result, nums, temp, visited);
            visited[i] = false;
            temp.remove(temp.size()-1);
        }
    }

依然是第二遍，依然不会做。。。

——2020.7.30