Leetcode#103 Binary Tree Zigzag Level Order Traversal

原题地址

基本数据结构操作，二叉树的层次遍历。

代码：

 vector<vector<int> > zigzagLevelOrder(TreeNode *root) {
         vector<vector<int> > res;
         vector<TreeNode *> layer;
         bool l2r = true;

         layer.push_back(root);
         while (!layer.empty()) {
             vector<TreeNode *> nextLayer;
             vector<int> path;
             for (auto node : layer) {
                 if (!node)
                     continue;
                 path.push_back(node->val);
                 nextLayer.push_back(node->left);
                 nextLayer.push_back(node->right);
             }
             if (!l2r) {
                 for (int i = ; (i << ) < path.size(); i++)
                     swap(path[i], path[path.size() - i - ]);
             }
             if (!path.empty())
                 res.push_back(path);
             layer = nextLayer;
             l2r = !l2r;
         }

         return res;
 }