题解 | #按之字形顺序打印二叉树#

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    vector<vector<int> > Print(TreeNode* pRoot) {
        if(!pRoot)    return {};

        vector<vector<int>> res;
        queue<TreeNode*> que;
        que.push(pRoot);
        int level = 1;
        while(!que.empty()) {
            int size = que.size();
            vector<int> vec;
            // 每一层节点的处理
            for(int i=0; i<size; i++) {
                TreeNode* node = que.front();    que.pop();
                vec.push_back(node->val);
                if(node->left)    que.push(node->left);
                if(node->right)    que.push(node->right);
            }
            // 奇偶层的判断，是否反转
            if(level%2 == 0)    reverse(vec.begin(), vec.end());
            level ++;
            // 收集结果
            res.push_back(vec);
        }
        return res;
    }
};