103. 二叉树的锯齿形层序遍历

原题链接：103. 二叉树的锯齿形层序遍历

solution:

        层序遍历,加一个reverse

class Solution {
public:
    vector> zigzagLevelOrder(TreeNode* root) {
        vector> res;    //定义返回值
        queue que;
        if(root != nullptr) que.push(root);
        bool flag = false;
        while(!que.empty()) {
            int size = que.size();
            vector path;
            while(size--) {
                auto t = que.front();
                que.pop();
                path.push_back(t->val);
                if(t->left != nullptr) que.push(t->left);
                if(t->right != nullptr) que.push(t->right);
            }
            if(flag) reverse(path.begin(),path.end());
            flag = !flag;
            res.push_back(path);
        }
        return res;
    }
};