LeetCode——sum-root-to-leaf-numbers

Question

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

递归遍历，到叶子节点就累加起来，然后需要用一个变量来记录路径中的值。

Code

class Solution {
public:
    int sumNumbers(TreeNode *root) {
        int total = 0;
        string path;
        sumNumbersCore(root, path, total);
        return total;
    }
    void sumNumbersCore(TreeNode* root, string path, int& total) {
        if (root != NULL) {
            // int 转 char
            path.push_back('0' + root->val);
            if (root->left != NULL)
            	sumNumbersCore(root->left, path, total);
            if (root->right != NULL)
            	sumNumbersCore(root->right, path, total);
            if (root->left == NULL && root->right == NULL) {
           		total += stoi(path);
        		path.pop_back();
            }
        }
    }
};