题目描述
Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
Example1:
Input: [1,2,3,null,5,null,4] Output: [1, 3, 4] Explanation:
1 <---
/ \
2 3 <---
\ \
5 4 <---
解题思路
- 层次遍历，如果此时的i == size - 1，表明是该层的最后一个节点 （从右往左看）
- 如果此时的i == 0，表示是第一个节点（可以从左往右看）
/**
* 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<int> rightSideView(TreeNode* root) {
vector<int> res;
if(root == NULL){
return res;
}
queue<TreeNode*> q;
q.push(root);
while(!q.empty()){
int size = q.size();
for(int i = 0; i < size; i++){
TreeNode* t = q.front();
q.pop();
if(i == size - 1){
res.push_back(t -> val);
}
if(t -> left){
q.push(t -> left);
}
if(t -> right){
q.push(t -> right);
}
}
}
return res;
}
};
