Given a collection of distinct integers, return all possible permutations.
Example:
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| Input: [1,2,3]
Output:
[
[1,2,3],
[1,3,2],
[2,1,3],
[2,3,1],
[3,1,2],
[3,2,1]
]
|
DFS
DFS即可. 使用一个boolean数组来标记nums[i]是否已经出现在list里面了
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| class Solution {
public List<List<Integer>> permute(int[] nums) {
boolean[] isTraversed = new boolean[nums.length];
List<Integer> curr = new ArrayList<>();
List<List<Integer>> ans = new ArrayList<>();
permute(ans, curr, nums, isTraversed);
return ans;
}
private void permute(List<List<Integer>> ans, List<Integer> curr, int[] nums, boolean[] isTraversed)
{
if(curr.size() == nums.length)
{
ans.add(new ArrayList<Integer>(curr));
return;
}
for(int i = 0; i < nums.length; ++i)
{
if(!isTraversed[i])
{
curr.add(nums[i]);
isTraversed[i] = true;
permute(ans, curr, nums, isTraversed);
curr.remove(curr.size() - 1);
isTraversed[i] = false;
}
}
}
}
|