Sum Root to Leaf Numbers

Sum Root to Leaf Numbers

 

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \
  2   3

 

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

 top-down 显然很直接.  可以改变每个node的值. 如果不想改变可以添加一个path.在函数参数里.

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