Boundary Of Binary Tree.cpp

class Solution {
public:
   
    //function to check if the node is leaf or not
    bool isLeaf(Node* root){
        return !root->left && !root->right;
    }
   
    //function to add the left boundary
    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;
        }
    }
   
    //function to add the left boundary and add it in reverse order
    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;
        }
       
        for(int i=temp.size()-1;i>=0;i--){
            ans.push_back(temp[i]);
        }
    }
   
    //add the leaf nodes
    void addLeaves(Node* root, vector<int>& ans){
        if(isLeaf(root)){
            ans.push_back(root->data);
            return;
        }
        if(root->left) addLeaves(root->left,ans);
        if(root->right) addLeaves(root->right,ans);
    }


    //main function
    vector <int> boundary(Node *root)
    {
        //Your code here
        vector<int>ans;
        if(root==NULL){
            return ans;
        }
        if(!isLeaf(root)){
            ans.push_back(root->data);
        }
        addLeftBoundary(root,ans);
        addLeaves(root,ans);
        addRightBoundary(root,ans);
        return ans;
    }

};