[LeetCode] 199. Binary Tree Right Side View

Binary Tree Right Side View

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.
Example:

Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:
1 <—
/ \
2 3 <—
\ \
5 4 <—

解析

树的层次遍历，并将每一层的最后一个节点值加入res。

代码

class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        queue<TreeNode*> q;
        vector<int> res;
        if(!root) return res;
        q.push(root);
        while(!q.empty()){
            int size = q.size();
            for(int i=0;i<size;i++){
                TreeNode* p = q.front();
                q.pop();
                if(i==size-1)
                    res.push_back(p->val);
                if(p->left) q.push(p->left);
                if(p->right) q.push(p->right);
            }
        }
        return res;
    }
};