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.
思路：这道题使用递归。这道题思路比较明确，目标是把从根到叶子节点的所有路径得到的整数累加起来，递归条件即是把当前的sum*10加上当前结点的值传入函数，进行递归，最终把左右子树的总和相加。结束条件就是如果一个结点是叶子结点，那么我们应该累加到结果总和中。
/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: int sumPath(TreeNode *root,int sum) { if(root==NULL) return 0; sum=sum*10+root->val; if(root->left==NULL&&root->right==NULL) { return sum; } if(root->left==NULL) return sumPath(root->right,sum); if(root->right==NULL) return sumPath(root->left,sum); return sumPath(root->left,sum)+sumPath(root->right,sum); } int sumNumbers(TreeNode *root) { int sum=0; return sumPath(root,sum); } };
Sum Root to Leaf Numbers,布布扣,bubuko.com
原文：http://www.cnblogs.com/awy-blog/p/3651063.html