LeetCode Algorithms #102 <Binary Tree Level Order Traversal>

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}

,

3
/ \
9  20
/  \
15   7

return its level order traversal as:

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

思路：
因为需要在迭代的时候插入层的信息，所以考虑再开一个函数进行迭代展开。

。。。

解：

/**
* 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 {
private:
vector<vector<int>> _resultVector;
public:
vector<vector<int>> levelOrder(TreeNode* root) {
addParticularLevel(root, 0);
return _resultVector;
}

void addParticularLevel(TreeNode* node, int level)
{
if(node == nullptr)
return;

if(level == _resultVector.size())
{
vector<int> particularLevelVals;
_resultVector.push_back(particularLevelVals);
}

_resultVector[level].push_back(node->val);
addParticularLevel(node->left, level+1);
addParticularLevel(node->right, level+1);
}
};