leetcode: Sum Root to Leaf Numbers

直接遍历所有路径将结果加起来即可。　　　优化空间有限、

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