题目描述:

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,

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2
3
4
  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.

简单的DFS获取所有从根节点到叶子节点的路径的问题.

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/**
 * 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) {
        if(!root) return 0;
        vector<int> sums;
        string path;
        getPath(root, path, sums);
        int sum = 0;
        for(int i = 0; i < sums.size(); i++){
            sum += sums[i];
        }
        return sum;
    }
    
    void getPath(TreeNode* root, string &path, vector<int> &sums){
        if(!root->left && !root->right){
            path.push_back(root->val + '0');
            sums.push_back(stoi(path));
            path.pop_back();
            return;
        }
        path.push_back(root->val + '0');
        if(root->left){
            getPath(root->left, path, sums);
        }
        if(root->right){
            getPath(root->right, path, sums);
        }
        path.pop_back();
    }
};