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[leetcode] 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.
思路：
又是dfs。有一个地方开始错了，只有当遍历到叶子节点时，在对最后的结果进行处理，所以dfs函数中需要一个变量保存当前层某个节点时的值（这里是num）。
** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public: void dfs(TreeNode *root, int num, int& res) { if(root->left==NULL && root->right==NULL) res = res + num*10 + root->val; if(root->left) dfs(root->left, num*10+root->val, res); if(root->right) dfs(root->right, num*10+root->val, res); } int sumNumbers(TreeNode *root) { int res = 0; if(root==NULL) return res; dfs(root, 0, res); return res; }};
[leetcode] Sum Root to Leaf Numbers
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