GFG PTOD | 08 Feb | Tree Boundary Traversal | Medium level | Tree

bool isLeaf(Node *root) {
        if(root->left == NULL && root->right == NULL)
            return true;
        return false;
    }
    void leftBoundry(Node *root, vector<int> &res) {
        if(root == NULL || isLeaf(root)) return;
        res.push_back(root->data);
        if(root->left) leftBoundry(root->left, res);
        else if(root->right) leftBoundry(root->right, res);
    }
    void leafBoundry(Node *root, vector<int> &res) {
        if(root == NULL) return;
        if(isLeaf(root)) {
            res.push_back(root->data);
            return;
        }
        leafBoundry(root->left, res);
        leafBoundry(root->right, res);
    }
    void rightBoundry(Node *root, vector<int> &res) {
        if(root == NULL || isLeaf(root)) return;
        if(root->right) rightBoundry(root->right, res); 
        else if(root->left) rightBoundry(root->left, res);
        res.push_back(root->data);
    }
    vector<int> boundaryTraversal(Node *root) {
        // code here
        vector<int> res;
        if(!root) return res;
        if(!isLeaf(root)) res.push_back(root->data);
        leftBoundry(root->left, res);
        leafBoundry(root, res);
        rightBoundry(root->right, res);
        
        return res;
    }