[Oracle] LeetCode 199 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.

Solution

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/**
 * 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 {
private:
    vector<int> ans;
    queue<TreeNode*> q;
public:
    vector<int> rightSideView(TreeNode* root) {
        if(!root)return ans;
        q.push(root);ans.push_back(root->val);
        while(!q.empty()){
            int sz = q.size();
            int fg=0;
            for(int i=0;i<sz;i++){
                auto f=q.front();q.pop();
                if(f->right){
                    if(!fg)ans.push_back(f->right->val),fg=1;
                    q.push(f->right);
                }
                if(f->left){
                    if(!fg)ans.push_back(f->left->val),fg=1;
                    q.push(f->left);
                }
            }
        }
        return ans;
    }
};