剑指OFFER 按之字形顺序打印二叉树

Posted 2021-03-14 virgildevil

剑指OFFER 按之字形顺序打印二叉树

套用 剑指OFFER?把二叉树打印成多行的代码,然后翻转一下奇数行即可

/*
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==NULL)return vector<vector<int> >();
        queue<pair<TreeNode*,int> > que;//结点,层数
        vector<vector<int> > res;//返回的结果
        map<int,vector<int> >m;//层数--该层的所有结点

        que.push(pair<TreeNode*,int>(pRoot,0));

        while(!que.empty())
        {
            pair<TreeNode*,int> p = que.front();
            que.pop();

            m[p.second].push_back(p.first->val);

            if(p.first->left!=NULL){
                que.push(pair<TreeNode*,int>(p.first->left,p.second+1));
            }
            if(p.first->right!=NULL){
                que.push(pair<TreeNode*,int>(p.first->right,p.second+1));
            }

        }
        auto it = m.begin();
        while(it != m.end())
        {
            res.push_back(it->second);
            it++;
        }
        
        for(int i=0;i<res.size();i++)
        {
            if(i%2!=0)reverse(res[i].begin(),res[i].end());
        }
        
        return res;
    }
    
};