LeetCode/L046_Permutations.java at master · listenbehind/LeetCode · GitHub

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package LeetCode;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class L046_Permutations {

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

		if (nums == null || nums.length == 0) {
			return new ArrayList<List<Integer>>();
		}

		ArrayList<List<Integer>> rt = new ArrayList<List<Integer>>();

		if (nums.length == 1) {
			rt.add(new ArrayList<Integer>(Arrays.asList(nums[0])));
		} else {

			for (int i = 0; i < nums.length; i++) {
				for (List<Integer> l : permute(resetof(nums, i))) {
					l.add(nums[i]);
					rt.add(l);
				}
			}
		}

		return rt;
	}

	private int[] resetof(int[] nums, int index) {

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

		int s = 0;
		for (int i = 0; i < nums.length; i++) {
			if (i != index) {
				rt[s++] = nums[i];
			}
		}

		return rt;
	}

}