所有求树的边界,最优都是O(N)的。
/**
* 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:
void dfs(TreeNode* now,vector<int>& ans,int level){
if(level >= ans.size()) ans.push_back(now->val);
else ans[level] = now->val;
if(now->left != NULL) dfs(now->left,ans,level+1);
if(now->right != NULL) dfs(now->right,ans,level+1);
}
vector<int> rightSideView(TreeNode* root) {
vector<int> ans;
if(root != NULL) dfs(root,ans,0);
return ans;
}
};