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<>();
        List<Integer> path = new ArrayList<>();
        boolean[] visited = new boolean[nums.length];
        dfs(nums, result, path, visited);
        return result;
    }
    
    private void dfs(int[] nums, List<List<Integer>> result, List<Integer> path, boolean[] visited) {
        if (path.size() == nums.length) {
            result.add(new ArrayList<>(path));
            return;
        }
        for (int i = 0; i < nums.length; i++) {
            if (visited[i]) {
                continue;
            }
            visited[i] = true;
            path.add(nums[i]);
            dfs(nums, result, path, visited);
            // backtrack
            path.remove(path.size() - 1);
            visited[i] = false;
        }
    }
}