Iterative Boundary Level Traversal of Binary tree

iterative_boundary_traversal.cpp

class Solution {
public:
    bool isLeaf(Node* root){
        return !root->left and !root->right;
    }
    void addLeftBoundary(Node* root, vector<int> &ans){
        Node* curr = root->left;
        while(curr){
            if(!isLeaf(curr)) ans.push_back(curr->data);
            if(curr->left) curr = curr->left;
            else curr = curr->right;
        }
    }
    void addLeaves(Node* root, vector<int> &ans){
        if(!root)
            return;
        if(isLeaf(root)){
            ans.push_back(root->data);
            return;   
        }
        addLeaves(root->left, ans);
        addLeaves(root->right, ans);
    }
    void addRightBoundary(Node* root, vector<int> &ans){
        Node* curr = root->right;
        vector<int> temp;
        while(curr){
            if(!isLeaf(curr)) temp.push_back(curr->data);
            if(curr->right) curr = curr->right;
            else curr = curr->left;
        }
        int n = temp.size();
        for(int i = n-1; i >= 0; i--){
            ans.push_back(temp[i]);
        }
    }
    
    vector <int> boundary(Node *root)
    {
        vector<int> ans;
        if(!root) return ans;
        if(!root->left and !root->right)
            return {root->data};
        ans.push_back(root->data);
        addLeftBoundary(root,ans);
        addLeaves(root,ans);
        addRightBoundary(root,ans);
        return ans;
    }
};