Leetcode: Binary Tree Zigzag Level Order Traversal

转载于 2013-12-11 09:34:00 发布 · 56 阅读

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本文介绍了一种实现二叉树锯齿形层级遍历的方法。通过使用双端队列记录节点，并根据层级奇偶性决定添加顺序，最终实现了按层且交错输出节点值的功能。

代码:

class Solution {
public:
    vector<vector<int> > zigzagLevelOrder(TreeNode *root) {
        
		
		vector<vector<int> > res;
		if(root == NULL)
			return res;
		
		vector<int> level;
		deque<TreeNode*> record;
		record.push_back(root);
		int cnt = 1, curcnt = 0;
		bool order = true;
		while(!record.empty()) {
			TreeNode *nxt = record.front();
			record.pop_front();
			level.push_back(nxt->val);
			
			if(nxt->left) {
				record.push_back(nxt->left);
				curcnt++;
			}
			if(nxt->right) {
				record.push_back(nxt->right);
				curcnt++;
			}

			cnt --;
			if(cnt == 0) {
				if(order) {		// 正序
					res.push_back(level);
				}else{
					reverse(level.begin(), level.end());
					res.push_back(level);
				}
				order = !order;
				level.clear();
				cnt = curcnt;
				curcnt = 0;
			}
		}
		return res;
    }
};