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.

/**
 * 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) {
        return inorder(root,0);
    }
    public int inorder(TreeNode root,int value){//root的parent传递下来的值
        if(root == null){
            return 0;
        }
        int tmp1=0,tmp2=0,tmp3=0;//tmp1为root代表的数，tmp2为left代表的数，tmp3为right代表的数
        tmp1 = value*10 + root.val;
        if(root.left == null && root.right == null){//叶子节点
            return tmp1;
        }
        //非叶子节点返回的是左右孩子节点之和
        if(root.left != null){
            tmp2 = inorder(root.left,tmp1);
        }
        if(root.right != null){
            tmp3 = inorder(root.right,tmp1);
        }
        return tmp2+tmp3;
    }
}

总体来说，这还是很简单的，一个遍历就可以实现。

Runtime: 218 ms

可能是网速快，所以运行的快，或许是leetcode计算运行时间采用的是运行时间=返回结果时间-提交时间