# 0366. Find Leaves of Binary Tree

<https://leetcode.com/problems/find-leaves-of-binary-tree>

## Description

Given the `root` of a binary tree, collect a tree's nodes as if you were doing this:

* Collect all the leaf nodes.
* Remove all the leaf nodes.
* Repeat until the tree is empty.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/03/16/remleaves-tree.jpg)

```
**Input:** root = [1,2,3,4,5]
**Output:** [[4,5,3],[2],[1]]
Explanation:
[[3,5,4],[2],[1]] and [[3,4,5],[2],[1]] are also considered correct answers since per each level it does not matter the order on which elements are returned.
```

**Example 2:**

```
**Input:** root = [1]
**Output:** [[1]]
```

**Constraints:**

* The number of nodes in the tree is in the range `[1, 100]`.
* `-100 <= Node.val <= 100`

## ac

```java
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<List<Integer>> findLeaves(TreeNode root) {
        Map<Integer, List<Integer>> map = new HashMap<>();
        dfs(root, map);

        List<List<Integer>> res = new ArrayList<>();
        for (int i = 1; i <= map.size(); i++) {
            res.add(map.get(i));
        }

        return res;
    }

    public int dfs(TreeNode node, Map<Integer, List<Integer>> map) {
        if (node == null) return 0;

        int left = dfs(node.left, map);
        int right = dfs(node.right, map);

        int dist = Math.max(left, right) + 1;
        map.putIfAbsent(dist, new ArrayList<>());
        map.get(dist).add(node.val);

        return dist;
    }
}

/*
1) dfs get distance to leaf, store in map; 2) iterate map, get result
*/
```


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