Permutations && Permutations ii

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Permutations 中不带有重复元素

Permutations II 中带有重复元素

Permutations

java

public class Solution {    /*     * @param nums: A list of integers.     * @return: A list of permutations.     */    public List<List<Integer>> permute(int[] nums) {        // write your code here        List<List<Integer>> result = new ArrayList<>();        if (nums == null || nums.length == 0) {            result.add(new ArrayList<Integer>());            return result;        }        List<Integer> path = new ArrayList<>();        Set<Integer> set = new HashSet<>();        dfs(nums, path, result, set);        return result;    }    private void dfs(int[] nums,                      List<Integer> path,                     List<List<Integer>> result,                     Set<Integer> set) {        if (path.size() == nums.length) {            result.add(new ArrayList<Integer>(path));            return;        }                  for (int i = 0; i < nums.length; i++) {            if (!set.contains(nums[i])) {                set.add(nums[i]);                path.add(nums[i]);                dfs(nums, path, result, set);                set.remove(nums[i]);                path.remove(path.size() - 1);            }        }    }}

Permutations II

java

public class Solution {    /*     * @param :  A list of integers     * @return: A list of unique permutations     */    public List<List<Integer>> permuteUnique(int[] nums) {        // write your code here        List<List<Integer>> result = new ArrayList<>();        if (nums == null || nums.length == 0) {            result.add(new ArrayList<Integer>());            return result;        }         List<Integer> path = new ArrayList<>();        boolean[] visit = new boolean[nums.length];        Arrays.sort(nums);        dfs(nums, path, result, visit);        return result;    }    private void dfs(int[] nums,                      List<Integer> path,                      List<List<Integer>> result,                     boolean[] visit) {        if (path.size() == nums.length) {            result.add(new ArrayList<Integer>(path));            return;        }                  for (int i = 0; i < nums.length; i++) {            if ((visit[i] == true) || (i != 0 && nums[i] == nums[i - 1] && visit[i - 1] == false)) {                continue;            } else {                path.add(nums[i]);                visit[i] = true;                dfs(nums, path, result, visit);                visit[i] = false;                path.remove(path.size() - 1);            }        }    }}

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