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] ]
用lev记录当前树到了第几层。
/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: vector<vector<int> > re; vector<vector<int> > levelOrder(TreeNode *root) { if(root == NULL)return re; level(root,1); return re; } void level(TreeNode *root, int lev) { if(root == NULL)return; if(lev > re.size()) { vector<int > temp; re.push_back(temp); } re[lev-1].push_back(root->val); level(root->left,lev+1); level(root->right,lev+1); } };