46.全排列

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

class Solution {
    public List<List<Integer>> permute(int[] nums) {

        List<List<Integer>> res = new LinkedList<>();
        List<Integer> record = new LinkedList<>();
        permute(res, record, nums);
        return res;
    }

    public void permute(List<List<Integer>> res ,List<Integer> record, int[] nums) {

        if (nums.length == 1) {
            record.add(nums[0]);
            res.add(record);
            return;
        }

        for (int i = 0; i < nums.length; i++) {
            int[] ints = removeIndex(nums, i);
            LinkedList<Integer> list = new LinkedList<>(record);
            list.add(nums[i]);
            permute(res, list, ints);
        }

    }

    public int[] removeIndex(int[] nums, int index) {

        int[] ints = new int[nums.length - 1];

        System.arraycopy(nums, 0, ints, 0, index);
        System.arraycopy(nums, index + 1, ints, index, nums.length - index - 1);

        return ints;
    }

}