题解 | #按之字形顺序打印二叉树#

1.队列法

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
#include<queue>

class Solution {
public:
    vector<vector<int>> Print(TreeNode* pRoot) {
        vector<vector<int>> res = vector<vector<int>>();
        queue<TreeNode*> q = queue<TreeNode*>();
        int mark = 1;
        if(pRoot) {
            q.push(pRoot);
        }
        while(!q.empty()) {
            vector<int> current = vector<int>();
            int n = q.size();
            for(int i =0;i<n;i++) {
                TreeNode* node = q.front();
                q.pop();
                current.push_back(node->val);
                if(node->left){
                    q.push(node->left);
                }
                if(node->right){
                    q.push(node->right);
                }
            }
            if(mark%2==0){
                reverse(current.begin(), current.end());
            }
            mark++;
            res.push_back(current);
        }
        return res;
    }
    
};