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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.

 

每到达一个根节点,就代表一个路径访问完成,将和加入总和。

树结构用递归是最容易的,每递归一层,上层的部分和需要乘以10在做加法。

/** * 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 sumNumbers(TreeNode *root) {        int Sum = 0;        Helper(root, 0, Sum);        return Sum;    }    void Helper(TreeNode* root, int partSum, int& Sum)    {        if(root == NULL)            return;        else if(root->left == NULL && root->right == NULL)  //add this path            Sum += (10*partSum+root->val);        else        {            Helper(root->left, 10*partSum+root->val, Sum);            Helper(root->right, 10*partSum+root->val, Sum);        }    }};

【LeetCode】Sum Root to Leaf Numbers