leetcode回溯-46

import java.util.LinkedList;
import java.util.List;

/**
<p>给定一个不含重复数字的数组 <code>nums</code> ，返回其 <em>所有可能的全排列</em> 。你可以 <strong>按任意顺序</strong> 返回答案。</p>

<p>&nbsp;</p>

<p><strong>示例 1：</strong></p>

<pre>
<strong>输入：</strong>nums = [1,2,3]
<strong>输出：</strong>[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
</pre>

<p><strong>示例 2：</strong></p>

<pre>
<strong>输入：</strong>nums = [0,1]
<strong>输出：</strong>[[0,1],[1,0]]
</pre>

<p><strong>示例 3：</strong></p>

<pre>
<strong>输入：</strong>nums = [1]
<strong>输出：</strong>[[1]]
</pre>

<p>&nbsp;</p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 6</code></li>
	<li><code>-10 &lt;= nums[i] &lt;= 10</code></li>
	<li><code>nums</code> 中的所有整数 <strong>互不相同</strong></li>
</ul>
<div><div>Related Topics</div><div><li>数组</li><li>回溯</li></div></div><br><div><li>👍 2073</li><li>👎 0</li></div>
*/

//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
	List<List<Integer>> res = new LinkedList<>();
	public List<List<Integer>> permute(int[] nums) {
		backtrack(nums,new LinkedList<>());
		return res;
	}

	//回溯，固定框架，类似多叉树遍历
	void backtrack(int[] nums,LinkedList<Integer> track){
		if(track.size()== nums.length){
			res.add(new LinkedList<>(track));
			return;
		}

		for (int i = 0; i < nums.length; i++) {
			if(track.contains(nums[i])){
				continue;
			}

			track.add(nums[i]);
			backtrack(nums,track);
			track.removeLast();
		}
	}


}
//leetcode submit region end(Prohibit modification and deletion)