正常层序遍历后翻转输出

/**
 * struct TreeNode {
 *    int val;
 *    struct TreeNode *left;
 *    struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param root TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > zigzagLevelOrder(TreeNode* root) {
        // write code here
        if (!root)
            return {};
        vector<vector<int> > ret;
        queue<TreeNode*> q;
        q.push(root);
        vector<int> tmp;
        while (!q.empty()) {
            tmp.clear();
            int currentSize = q.size();
            for (int i = 0; i < currentSize; i++) {
                TreeNode *node = q.front();
                q.pop();
                tmp.push_back(node->val);
                if (node->left)
                    q.push(node->left);
                if (node->right)
                    q.push(node->right);
            }
            ret.push_back(tmp);
        } //层序遍历

        //翻转Z型
        for (int i = 0; i < ret.size(); i++)
            if (i & 1 != 0)
                reverse(ret[i].begin(), ret[i].end());
        return ret;

    }
};