Burn tree

class Solution {
  public:
  
    Node* createParentMapping(Node* root, int target, map<Node*,Node*> &nodeToParent){
        Node* res = NULL;
        queue<Node*> q;
        q.push(root);
        nodeToParent[root] = NULL;
        while(!q.empty()){
            Node* frontNode = q.front();
            q.pop();
            if(frontNode->data == target){
                res = frontNode;
            }
            if(frontNode->left){
                nodeToParent[frontNode->left] = frontNode;
                q.push(frontNode->left);
            }
            if(frontNode->right){
                nodeToParent[frontNode->right] = frontNode;
                q.push(frontNode->right);
            }
        }
        return res;
    }
  
    int burnTree(Node* root, map<Node*,Node*> &nodeToParent){
        map<Node*, bool> visited;
        queue<Node*> q;
        q.push(root);
        visited[root] = true;
        int ans = 0;
        while(!q.empty()){
            bool flag = false;
            int size = q.size();
            for(int i=0;i<size;i++){
                //process the neighboring node
                Node* frontNode = q.front();
                q.pop();
                if(frontNode->left && !visited[frontNode->left]){
                    flag = true;
                    q.push(frontNode->left);
                    visited[frontNode->left] = true;
                }
                if(frontNode->right && !visited[frontNode->right]){
                    flag = true;
                    q.push(frontNode->right);
                    visited[frontNode->right] = true;
                }
                if(nodeToParent[frontNode] && !visited[nodeToParent[frontNode]]){
                    flag = true;
                    q.push(nodeToParent[frontNode]);
                    visited[nodeToParent[frontNode]] = true;
                }
            }
            if(flag == 1){
                ans++;
            }
        }
        return ans;
    }
  
    int minTime(Node* root, int target) 
    {
        map<Node*,Node*> nodeToParent;
        Node* targetNode = createParentMapping(root,target,nodeToParent);
        int ans = burnTree(targetNode,nodeToParent);
        return ans;
    }
};