Integer array Permutations

permutations.java

class Solution {
    public List<List<Integer>> permute(int[] nums) {
        return permute(nums, 0, nums.length - 1);
    }
    
    private List<List<Integer>> permute(int[] nums, int low, int high) {
        List<List<Integer>> result = new ArrayList<List<Integer>>();
        if (low == high) {
            ArrayList<Integer> temp = new ArrayList<Integer>();
            temp.add(nums[low]);
            result.add(temp);
            return result;
        }
        
        int curr = nums[low];
        List<List<Integer>> permutations = permute(nums, low + 1, high);
        
        for(List<Integer> perm: permutations) {
            perm.add(0, curr);
            result.add(new ArrayList<Integer>(perm));
            
            for (int i = 0; i < perm.size() - 1; i++) {
                Integer t = perm.get(i);
                perm.set(i, perm.get(i+1));
                perm.set(i+1, t);
                result.add(new ArrayList<Integer>(perm));
            }
        }
        return result;
    }
}