题解 | #二叉树根节点到叶子节点的所有路径和#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 * }
 */

public class Solution {
    
    public int total = 0;
    
    /**
     * 
     * @param root TreeNode类 
     * @return int整型
     */
    public int sumNumbers (TreeNode root) {
        // write code here
        if (null == root) {
            return 0;
        }
        process(root, "");
        return total;
    }
    
    public void process(TreeNode node, String str) {
        
        str += node.val;
        
        if (null == node.left && null == node.right) {
            total += Integer.valueOf(str);
            return;
        }
        
        if (null != node.left) {
            process(node.left, str);
        }
        if (null != node.right) {
            process(node.right, str);
        }
        
        str.substring(0, str.length() - String.valueOf(node.val).length());
    }
}