Sum Root to Leaf Numbers-优快云博客

本文介绍了一种解决二叉树中所有从根到叶子节点路径数字之和的方法。通过递归遍历的方式，实现了计算所有可能路径所代表数字的总和，并给出了具体的Java实现示例。

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;
    }
}