binary_tree_right_side_view.cpp

// =====================================================================================
//
//       Filename:  binary_tree_right_side_view.cpp
//
//    Description:  199. 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.
//
//        Version:  1.0
//        Created:  09/11/2019 07:47:47 PM
//       Revision:  none
//       Compiler:  g++
//
//         Author:  Zhu Xianfeng (), xianfeng.zhu@gmail.com
//   Organization:  
//
// =====================================================================================
#include <stdio.h>
#include <queue>
#include <vector>

struct TreeNode
{
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution
{
public:
    std::vector<int> rightSideView(TreeNode* root)
    {
        if (root == nullptr)
        {
            return std::vector<int>();
        }

        std::vector<int> values;
        std::queue<TreeNode*> nodes;

        nodes.push(root);
        while (!nodes.empty())
        {
            values.push_back(nodes.back()->val);
            int len = nodes.size();
            while (len > 0)
            {
                auto* cur = nodes.front();
                if (cur->left != nullptr)
                {
                    nodes.push(cur->left);
                }
                if (cur->right != nullptr)
                {
                    nodes.push(cur->right);
                }

                nodes.pop();
                len--;
            }
        }

        return values;
    }
};

int main(int argc, char* argv[])
{
    TreeNode* root = nullptr;
    auto values = Solution().rightSideView(root);
    printf("Tree's height = %lu\n", values.size());
    return 0;
}