AcWing 44. 分行从上往下打印二叉树
原题链接
中等
作者:
daniellee
,
2019-04-10 20:37:27
,
所有人可见
,
阅读 875
算法1
(层级遍历) $O(n)$
C++ 代码
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int>> printFromTopToBottom(TreeNode* root) {
vector<vector<int>> v;
if (root==NULL) return v;
// cout<<v.size();
queue<TreeNode*> q;
q.push(root);
map<TreeNode*,int> level;
level[root] = 0;
while(!q.empty()){
TreeNode* c = q.front();
int l = level[c];
q.pop();
if (l==v.size()){
vector<int> v1;
v1.push_back(c->val);
v.push_back(v1);
}
else{
v[l].push_back(c->val);
}
if (c->left!=NULL){
q.push(c->left);
level[c->left] = l+1;
}
if (c->right!=NULL){
q.push(c->right);
level[c->right] = l+1;
}
}
return v;
}
};