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Permutations.java
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Permutations.java
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package by.andd3dfx.common;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* <pre>
* <a href="https://leetcode.com/problems/permutations/">Task description</a>
*
* Given an array nums of distinct integers, return all the possible permutations.
* You can return the answer in any order.
*
* Example 1:
*
* Input: nums = [1,2,3]
* Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
*
* Example 2:
*
* Input: nums = [0,1]
* Output: [[0,1],[1,0]]
*
* Example 3:
*
* Input: nums = [1]
* Output: [[1]]
* </pre>
*
* @see <a href="https://youtu.be/PyRnm2mFZbk">Video solution</a>
*/
public class Permutations {
public static List<List<Integer>> permute(int[] nums) {
List<List<Integer>> result = new ArrayList<>();
populate(result, 0, nums);
return result;
}
private static void populate(List<List<Integer>> result, int start, int[] nums) {
if (start == nums.length) {
result.add(toList(nums));
return;
}
for (int k = start; k < nums.length; k++) {
swap(nums, start, k);
populate(result, start + 1, nums);
swap(nums, start, k);
}
}
private static List<Integer> toList(int[] nums) {
return Arrays.stream(nums).boxed().toList();
}
private static void swap(int[] nums, int i, int j) {
var tmp = nums[i];
nums[i] = nums[j];
nums[j] = tmp;
}
}