LeetCode #366. Find Leaves of Binary Tree

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本文介绍了一种算法，用于对二叉树的节点进行分层收集并移除叶子节点，直至树为空。通过实例展示算法过程，如输入二叉树[1,2,3,4,5]，输出结果为[[4,5,3],[2],[1]]，解释了算法如何逐步移除并收集叶子节点。

题目描述：

Given a binary tree, collect a tree's nodes as if you were doing this: Collect and remove all leaves, repeat until the tree is empty.

Example:

Input: [1,2,3,4,5]
  
          1
         / \
        2   3
       / \     
      4   5    

Output: [[4,5,3],[2],[1]]

Explanation:

1. Removing the leaves [4,5,3] would result in this tree:

          1
         / 
        2

2. Now removing the leaf [2] would result in this tree:

3. Now removing the leaf [1] would result in the empty tree:

[]

class Solution {
public:
    vector<vector<int>> findLeaves(TreeNode* root) {
        vector<vector<int>> result;
        height(root,result);
        return result;
    }
    
    int height(TreeNode* root, vector<vector<int>>& result)
    {
        if(root==NULL) return 0;
        int h=max(height(root->left,result),height(root->right,result))+1;
        if(result.size()<h) result.resize(h);
        result[h-1].push_back(root->val);
        return h;
    }
};