LeetCode: Sum Root to Leaf Numbers

Given a binary tree containing digits from0-9Only, each root-to-leaf path

Cocould represent a number.

An example is the root-to-leaf path1->2->3Which represents the number123.

Find the total sum of all root-to-leaf numbers.

For example,

    1   / \  2   3 

The root-to-leaf path1->2Represents the number12.

The root-to-leaf path1->3Represents the number13.

Return the sum = 12 + 13 =25.

Solution:

Traverse the binary tree to know the number of root-to-leaf nodes. Because the data is weak, the number on the path is used

Int can be saved. For example, if the depth of a fruit tree is greater than 10, int will overflow. Therefore, it is better to use a string,

Then simulate the addition operation.

Solution code:

/** * 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 *rt,int path,int &sum)    {        if (!rt) return ;        path = path * 10 + rt->val ;        if (rt->left == rt->right && !rt->left)            sum +=path;        dfs(rt->left,path,sum);        dfs(rt->right,path,sum);    }    int sumNumbers(TreeNode *root)     {        int ans = 0 ;        dfs(root,0,ans);        return ans ;    }};