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) {
    }
};
*/
#include <cstddef>
class Solution {
public:
    vector<vector<int> > Print(TreeNode* pRoot) {
        vector<vector<int>> res;
        queue<TreeNode *> q;
        if(!pRoot) return res;
        int count = 0;
        q.push(pRoot);
        while(!q.empty()){
            vector<int> ans;
            count ++;
            int size = q.size();
            for(int i = 0;i < size;i ++){
                cout << i << " ";
                if(q.front() -> left) q.push(q.front()->left);
                if(q.front() -> right) q.push(q.front()->right);
                if(count % 2 == 1){
                    ans.push_back(q.front() -> val);
                }
                else if(count % 2 == 0){
                    ans.insert(ans.begin(),q.front() -> val);
                }
                q.pop();
            }
            res.push_back(ans);
        }
        return res;
    }
    
};

重写这道题，发现把q.size（）写到for里面去了，for里面又在操作q，导致出错。