java-Sum Root to Leaf Numbers

标签：depth-first search   递归   tree   

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.

以根节点到树叶为一路径 路径上节点值组成一个数 求所有数的和 是典型的深度优先遍历 但是每次进行递归时需要把已经得到的结果传过去 所以另外构造函数 传入 total值 若然后子叶则total*10+root.val继续递归 代码如下：

/**
 * 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 sum(0,root);
    }
    public int sum(int total,TreeNode root){
        if(root==null) return 0;
        if(root.left==null&&root.right==null){
            return total*10+root.val;      
        }else{              
            return sum(total*10+root.val,root.left)+sum(total*10+root.val,root.right);
        }
    }
}

java-Sum Root to Leaf Numbers

标签：depth-first search   递归   tree   

原文地址：http://blog.csdn.net/u012734829/article/details/42493119