LeetCode:Sum Root to Leaf Numbers

Sum Root to Leaf Numbers

Total Accepted: 78569  Total Submissions: 237646  Difficulty: Medium

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.

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思路：

DFS。

c++ code:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode* root) {
        return sumNumbers(root, 0);
    }
    
    // 自定义函数
    int sumNumbers(TreeNode* root, int sum) {
        if(!root) return 0;
        int tmp = sum * 10 + root->val;
        if(!root->left && !root->right) return tmp;
        return sumNumbers(root->left, tmp) + sumNumbers(root->right, tmp);
    }
};