Binary Tree Right Side View - Medium - NL
Published:
Question
- https://leetcode.com/problems/binary-tree-right-side-view/
Given the root of 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.
Approach
- bfs with queue and height.
Solution
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
vector<int> rightSideView(TreeNode* root) {
vector<int> ans;
if (root == NULL) {
return ans;
}
queue<pair<TreeNode*, int> > q;
q.push(make_pair(root, 0));
int h = -1;
while(!q.empty()) {
TreeNode* t = q.front().first;
int h1 = q.front().second;
q.pop();
if (h1 > h) {
ans.push_back(t->val);
h = h1;
}
if(t->right!=NULL) {
q.push(make_pair(t->right, h1+1));
}
if(t->left!=NULL) {
q.push(make_pair(t->left, h1+1));
}
}
return ans;
}
};