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[leetcode] problem 46 – permutations

admin 11月 13, 2020 0

Given a collection of distinct integers, return all possible permutations.

Example

Input: [1,2,3]

Output:

[
  [1,2,3],
  [1,3,2],
  [2,1,3],
  [2,3,1],
  [3,1,2],
  [3,2,1]
]

Code

public List<List<Integer>> permute(int[] nums) {
    List<List<Integer>> result = new ArrayList<>();

    permuteHelper(result, new ArrayList<>(), nums);

    return result;
}

private void (List<List<Integer>> result, List<Integer> permute, int[] nums) {
    if (permute.size() == nums.length) {
        result.add(new ArrayList<>(permute));
        return;
    }

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

        permute.add(nums[i]);
        permuteHelper(result, permute, nums);
        permute.remove(permute.size() - 1);
    }
}