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) {
        vector<vector<int>> res;
        vector<int> item;
        if(!pRoot) return res;
        queue<TreeNode*> q;
        TreeNode* node;
        q.emplace(pRoot);
        int size;
        while((size = q.size())!=0){
            while(size--){
                node = q.front();
                q.pop();
                item.push_back(node->val);
                if(node->left)
                    q.emplace(node->left);
                if(node->right)
                    q.emplace(node->right);
            }
            if(res.size()%2){
                reverse(item.begin(), item.end());
            }
            res.push_back(item);
            item.clear();
        }
        return res;
    }
};