199. Binary Tree Right Side View.cpp

#include <vector>
#include <queue>
using namespace std;
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> r;
        queue<TreeNode *> q;
        if (!root)
            return r;
        q.push(root);
        while (!q.empty())
        {
            int sz = q.size();
            for (int i = 0; i < sz; i++)
            {
                auto cur = q.front();
                q.pop();
                if (i == sz - 1)
                    r.push_back(cur->val);
                if (cur->left)
                    q.push(cur->left);
                if (cur->right)
                    q.push(cur->right);
            }
        }
        return r;
    }
};