LeetCode Q102: 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]
]

Solution:

	/**
	* 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>> levelOrder(TreeNode* root) {
	vector<vector<int> > res;
	if(root==NULL)
	return res;
	queue<TreeNode*> H;
	H.push(root);
	int cur=1;
	int next=0;
	vector<int> C;
	while(!H.empty()){
	TreeNode* front=H.front();
	H.pop();
	if(front!=NULL){
	C.push_back(front->val);
	H.push(front->left);
	H.push(front->right);
	next+=2;
	}
	cur--;
	if(cur==0&&!C.empty()){
	res.push_back(C);
	C.clear();
	cur=next;
	next=0;
	}
	}
	return res;
	}
	};

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