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Permutations.java
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Permutations.java
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import java.util.ArrayList;
import java.util.List;
/*
* https://leetcode.com/problems/permutations/
*/
public class Permutations {
public List<List<Integer>> permute(int[] nums) {
return permute(nums, new boolean[nums.length], new ArrayList<>());
}
private List<List<Integer>> permute(int[] nums, boolean[] visited, List<Integer> current) {
if (current.size() == nums.length) {
List<List<Integer>> lists = new ArrayList<>();
lists.add(new ArrayList<>(current));
return lists;
}
List<List<Integer>> ans = new ArrayList<>();
for (int i = 0; i < visited.length; i++) {
if (visited[i]) {
continue;
}
visited[i] = true;
current.add(nums[i]);
ans.addAll(permute(nums, visited, current));
visited[i] = false;
current.remove(Integer.valueOf(nums[i]));
}
return ans;
}
public static void main(String[] args) {
System.out.println(new Permutations().permute(
new int[]{1, 2, 3}
)); // [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
}
}