1. Topic introduction
Given a binary tree, imagine yourself standing on the right side of it, and return the node values that can be seen from the right side in order from top to bottom.
Example:
Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:
1 <---
/ \
2 3 <---
\ \
5 4 <---
Source: LeetCode
Link: https://leetcode-cn.com/problems/binary-tree-right-side-view The
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Two, problem-solving ideas
- Traverse the binary tree by layer, and save the rightmost node value of each layer to the output array, which is the right view of the binary tree.
Three, problem-solving code
/**
* 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> vec;
if(!root)
return vec;
queue<TreeNode*> que;
que.push(root);
while(!que.empty())
{
int len = que.size();
for(int i = 0; i < len; ++i)
{
TreeNode* node = que.front();
que.pop();
if(i == len-1)
vec.push_back(node->val);
if(node->left)
que.push(node->left);
if(node->right)
que.push(node->right);
}
}
return vec;
}
};Four, problem-solving results
