LEETCODE--Binary Tree Level Order Traversal

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本文介绍了一种解决二叉树层次遍历问题的方法。通过递归的方式，按层级顺序从左到右收集节点值。示例代码展示了如何实现这一算法，并给出了具体的二叉树示例及其层次遍历结果。

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Given a binary tree, return the level order traversal of its nodes’ values. (ie, from left to right, level by level).

For example:
Given binary tree {3,9,20,#,#,15,7},

/ \
9 20
/ \
15 7

return its level order traversal as:

[
[3],
[9,20],
[15,7]
]

confused what “{1,#,2,3}” means? > read more on how binary tree is serialized on OJ.

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
   vector<vector<int>> finsh;
    void levelsort(TreeNode* root, int level){
        if(!root)
          return ;
        if(level == finsh.size())
         {
            vector<int> add;
            finsh.push_back(add);
         }
        finsh[level].push_back(root->val);
        levelsort(root->left, level+1);
        levelsort(root->right, level+1);
    }

    vector<vector<int>> levelOrder(TreeNode* root) {
        levelsort(root, 0);
        return finsh;
    }
};