sumRootToLeafNumbers.java

/**
 * Definition for binary tree
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode(int x) { val = x; }
 * }
 */
 
public class Solution {
 
 public int dfs(TreeNode root, int sum) {
 if(root==null) {
 return 0;
 }
 if(root.left==null&&root.right==null) {
 return 10*sum + root.val;
 }
 int result = 0;
 if(root.left!=null) {
 result += dfs(root.left, 10*sum + root.val);
 }
 if(root.right!=null) {
 result += dfs(root.right, 10*sum + root.val);
 }
 return result;
 
 }
 public int sumNumbers(TreeNode root) {
 return dfs(root,0);
 }
}