diff --git a/Main.java b/Main.java index 1a68b2dd0a36d3447eed91dc217b0ec3bb12c172..f620e1da9cc637fcc56ffba4b43c8235057ba659 100644 --- a/Main.java +++ b/Main.java @@ -1,5 +1,11 @@ -class Main { +import java.util.ArrayList; +import java.util.Arrays; + +public class Main { public static void main(String[] args) { - System.out.println("Hello world!"); + + int[] arr = {1, 2, 3}; + ArrayList> result = Permutations.permute(arr); + System.out.println(result); } } \ No newline at end of file diff --git a/Permutations.java b/Permutations.java new file mode 100644 index 0000000000000000000000000000000000000000..0df77928cc11572ed831a1e8a56d1883c040fd94 --- /dev/null +++ b/Permutations.java @@ -0,0 +1,39 @@ +import java.util.ArrayList; +import java.util.Arrays; + +public class Permutations { + public static void main(String[] args) { + int[] arr = {1, 2, 3}; + ArrayList> result = permute(arr); + System.out.println(result); + } + + public static ArrayList> permute(int[] nums) { + ArrayList> result = new ArrayList<>(); + if (nums == null || nums.length == 0) { + return result; + } + ArrayList list = new ArrayList(); + Arrays.sort(nums); + boolean[] used = new boolean[nums.length]; + helper(result, list, nums, used); + return result; + } + + public static void helper(ArrayList> result, ArrayList list, int[] nums, boolean[] used) { + if (list.size() == nums.length) { + result.add(new ArrayList(list)); + return; + } + for (int i = 0; i < nums.length; i++) { + if (used[i] || (i > 0 && nums[i] == nums[i - 1] && !used[i - 1])) { + continue; + } + used[i] = true; + list.add(nums[i]); + helper(result, list, nums, used); + used[i] = false; + list.remove(list.size() - 1); + } + } +}