把二叉树打印成多行

题目描述

从上到下按层打印二叉树，同一层结点从左至右输出。每一层输出一行。

 

思路：把上题的打印成之字形的根据层数决定是否逆转去掉就行。

/*
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>> vv;
            vector<int> v;
            queue<TreeNode*> q;
            if(!pRoot) return vv;
            TreeNode* last = pRoot,*c,*lastc;
            q.push(pRoot);
            int i = 0,value = 0;
            while(!q.empty())
            {
                while(!q.empty()&&q.front()!=last)
                {
                    c = q.front();
                    value = c->val;
                    v.push_back(value);
                    if(c->left) q.push(c->left);
                    if(c->right) q.push(c->right);
                    q.pop();
                }
                if(q.front()==last)
                {
                    v.push_back(last->val);
                    if(last->left)
                    {
                        q.push(last->left);
                        lastc = last->left;
                    }
                    if(last->right)
                    {
                        q.push(last->right);
                        lastc = last->right;
                    }
                    q.pop();
                    last = lastc;
                }
                i++;
                vv.push_back(v);
                v.clear();
            }
            return vv;
        }
    
};