SDE-Challenge/Binary-Tree-Right-Side-View.cpp at main · looneyd-rohit/SDE-Challenge · GitHub

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// Leetcode 199
/**
 * 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 {
public:
    vector<int> rightSideView(TreeNode* root) {
        // queue based approach (for loop inside):
        vector<int> ans;
        if(root == NULL) return ans;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            int sz = q.size();
            int last = -1;
            while(sz--){
                auto f = q.front(); q.pop();
                last = f->val;
                TreeNode* left = f->left;
                if(left) q.push(left);
                TreeNode* right = f->right;
                if(right) q.push(right);
            }
            ans.push_back(last);
        }
        return ans;
    }
};