* Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
              
 */
public class Solution {
    public bool HasPathSum(TreeNode root, int sum) {
         if(root == null) return false;
         Stack<TreeNode> st = new Stack<TreeNode>();
          st.Push(root);
          int pathsum = 0;
          
        while(st.Any())
        {
            TreeNode curr = st.Pop();
           
            if(curr!= null)
            {
               pathsum = pathsum + curr.val; 
            }
            
            if(curr.left != null)
            {
                st.Push(curr.left);
            }
            
             if(curr.right != null)
            {
                st.Push(curr.right);
            }
            
            
            if(pathsum == sum && curr.left == null && curr.right == null) return true;
            
            if(curr.left == null && curr.right == null)
            {
                pathsum = root.val;
            }
            
            
        }
        
        return  false;
        
        
         
        
        
    }
}```