Binary Tree Right Side View Solutions in C++

// Source : https://leetcode.com/problems/binary-tree-right-side-view/
// Author : Hao Chen
// Date   : 2015-04-07



/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void rightSideViewHelper(TreeNode* root, int level, vector<int>& result) {
        if (root == NULL) return;
        if ( result.size() < level ) result.push_back(root->val);
        rightSideViewHelper(root->right, level+1, result);
        rightSideViewHelper(root->left, level+1, result);
    }
    
    void rightSideViewHelper(TreeNode* root, vector<int>& result) {
        if (root==NULL) return;

        vector<TreeNode*> stack;
        vector<int> level;
        stack.push_back(root);
        level.push_back(1);
        
        while (stack.size()>0) {
            TreeNode* r = stack.back(); stack.pop_back();
            int l = level.back(); level.pop_back();
            if ( result.size() < l ) {
                result.push_back(r->val);
            }
            if (r->left) {
                stack.push_back(r->left);
                level.push_back(l+1);
            }
            if (r->right) {
                stack.push_back(r->right);
                level.push_back(l+1);
            }
        }
    }
    vector<int> rightSideView(TreeNode *root) {
        vector<int> result;
        if (rand()%2){
            rightSideViewHelper(root, 1, result);
        }else{
            rightSideViewHelper(root, result);
        }
        return result;
    }
};

/// Source : https://leetcode.com/problems/binary-tree-right-side-view/
/// Author : liuyubobobo
/// Time   : 2019-09-26

#include <iostream>
#include <vector>

using namespace std;


/// BFS
/// Time Complexity: O(n)
/// Space Complexity: O(n)

/// 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> res;
        if(!root) return res;

        vector<TreeNode*> cur = {root};
        while(cur.size()){
            res.push_back(cur.back()->val);

            vector<TreeNode*> next;
            for(TreeNode* node: cur){
                if(node->left) next.push_back(node->left);
                if(node->right) next.push_back(node->right);
            }
            cur = next;
        }
        return res;
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/binary-tree-right-side-view/
/// Author : liuyubobobo
/// Time   : 2019-09-26

#include <iostream>
#include <vector>

using namespace std;


/// DFS
/// Time Complexity: O(n)
/// Space Complexity: O(h)

/// 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 {

private:
    vector<int> res;

public:
    vector<int> rightSideView(TreeNode* root) {

        if(!root) return res;

        dfs(root, 0);
        return res;
    }

private:
    void dfs(TreeNode* node, int d){

        if(res.size() <= d) res.push_back(0);
        res[d] = node->val;

        if(node->left) dfs(node->left, d + 1);
        if(node->right) dfs(node->right, d + 1);
    }
};


int main() {

    return 0;
}