4647784

Posted 2021-09-09 保护眼睛

dfs + 剪枝

• • • 784. 字母大小写全排列
    • 46.全排列
    • 47.全排列II

784. 字母大小写全排列

class Solution47 {
    public static void main(String[] args) {
        permuteUnique(new int[]{1, 2, 3});
        res.forEach(System.out::println);
    }

    static List<List<Integer>> res = new LinkedList<>();


    public static List<List<Integer>> permuteUnique(int[] nums) {
        LinkedList<Integer> cur = new LinkedList<>();
        boolean[] visited = new boolean[nums.length];
        Arrays.sort(nums);
        dfs(nums, res, cur, visited, 0);

        return res;
    }

    public static void dfs(int[] nums, List<List<Integer>> res, LinkedList<Integer> cur, boolean[] visited, int index) {
        if (cur.size() == nums.length) {
            res.add(new ArrayList<>(cur));
            return;
        }

        for (int i = 0; i < nums.length; i++) {
            if (visited[i]) {
                continue;
            }

            if (i > 0 && nums[i] == nums[i - 1] && !visited[i - 1]) {
                continue;
            }

            cur.add(nums[i]);
            visited[i] = true;

            dfs(nums, res, cur, visited, index + 1);

            cur.removeLast();
            visited[i] = false;
        }
    }
}

46.全排列

class Solution083 {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> res = new ArrayList<>();
        List<Integer> cur = new ArrayList<>();
        boolean[] visited = new boolean[nums.length];

        dfs(nums, res, cur, visited);

        return res;
    }

    public void dfs(int[] nums, List<List<Integer>> res, List<Integer> cur, boolean[] visited) {
        if (nums.length == cur.size()) {
            res.add(new ArrayList<>(cur));
            return;
        }

        for (int i = 0; i < nums.length; i++) {
            if (visited[i]) continue;
            cur.add(nums[i]);
            visited[i] = true;
            dfs(nums, res, cur, visited);
            cur.remove(cur.size() - 1);
            visited[i] = false;
        }
    }
}

47.全排列II

class Solution47 {
    public static void main(String[] args) {
        permuteUnique(new int[]{1, 2, 3});
        res.forEach(System.out::println);
    }

    static List<List<Integer>> res = new LinkedList<>();


    public static List<List<Integer>> permuteUnique(int[] nums) {
        LinkedList<Integer> cur = new LinkedList<>();
        boolean[] visited = new boolean[nums.length];
        Arrays.sort(nums);
        dfs(nums, res, cur, visited, 0);

        return res;
    }

    public static void dfs(int[] nums, List<List<Integer>> res, LinkedList<Integer> cur, boolean[] visited, int index) {
        if (cur.size() == nums.length) {
            res.add(new ArrayList<>(cur));
            return;
        }

        for (int i = 0; i < nums.length; i++) {
            if (visited[i]) {
                continue;
            }

            if (i > 0 && nums[i] == nums[i - 1] && !visited[i - 1]) {
                continue;
            }

            cur.add(nums[i]);
            visited[i] = true;

            dfs(nums, res, cur, visited, index + 1);

            cur.removeLast();
            visited[i] = false;
        }
    }
}