题目:
给定一个没有重复数字的序列,返回其所有可能的全排列
示例 1:
输入: [1,2,3]
输出:
[
[1,2,3],
[1,3,2],
[2,1,3],
[2,3,1],
[3,1,2],
[3,2,1]
]
代码1:
class Solution {
public List<List<Integer>> permute(int[] nums) {
List<List<Integer>> list = new ArrayList<>();
helper(list, nums, 0);
return list;
}
private void helper(List<List<Integer>> list, int[] nums, int n) {
if (n == nums.length - 1) {
list.add(asList(nums));
} else {
for (int i = n; i < nums.length; i++) {
swap(nums, n, i);
helper(list, nums, n + 1);
swap(nums, n, i);
}
}
}
private List<Integer> asList(int[] nums) {
List<Integer> list = new ArrayList<>(nums.length);
for (int i : nums) {
list.add(i);
}
return list;
}
private void swap(int[] arr, int i, int j) {
int c = arr[i];
arr[i] = arr[j];
arr[j] = c;
}
}