Day-26 Sum Root to Leaf Numbers

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int sumNumbers(TreeNode root) {
        return helper(root,0);
    }
    
    int helper(TreeNode node,int tempSum){
        if(node==null) return 0;
        if(node.left==null && node.right==null) {
            return tempSum*10+node.val;
        }
        return helper(node.left,tempSum*10+node.val) + helper(node.right,tempSum*10+node.val);
    }
} 

class Solution {
  public int sumNumbers(TreeNode root) {
    int rootToLeaf = 0, currNumber = 0;
    int steps;
    TreeNode predecessor;

    while (root != null) {
      if (root.left != null) {
        predecessor = root.left;
        steps = 1;
        while (predecessor.right != null && predecessor.right != root) {
          predecessor = predecessor.right;
          ++steps;
        }
        if (predecessor.right == null) {
          currNumber = currNumber * 10 + root.val;
          predecessor.right = root;
          root = root.left;
        }
        else {
          if (predecessor.left == null) {
            rootToLeaf += currNumber;
          }
          for(int i = 0; i < steps; ++i) {
            currNumber /= 10;
          }
          predecessor.right = null;
          root = root.right;
        }
      }
      else {
        currNumber = currNumber * 10 + root.val;
        if (root.right == null) {
          rootToLeaf += currNumber;
        }
        root = root.right;
      }
    }
    return rootToLeaf;
  }
}