Leetcode---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.

题目算简单的，关键在于正确区分

root==NULL和（root->left==NULL && root->right==NULL）这两种情况。

另外注意，树的遍历就是DFS----除了层序遍历外

void dfs(TreeNode *root, int& sum, int path){
    if(root==NULL)
        return;
    path=path*10+root->val;
    if(root->left==NULL && root->right==NULL){
        sum+=path;
        return;
    }
    dfs(root->left, sum, path);
    dfs(root->right, sum, path);
}

int sumNumbers(TreeNode *root) {
    int sum=0;
    int path=0;
    dfs(root, sum, path);
    return sum;
}

Leetcode---Sum Root to Leaf Numbers

原文：http://blog.csdn.net/ffmpeg4976/article/details/44903783