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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 3The 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.
思路：本题本质上是要对二叉树进行遍历。我们使用递归对二叉树进行深度优先遍历。
1 class Solution { 2 public: 3 int sumNumbers( TreeNode *root ) { 4 if( !root ) { return 0; } 5 return sumSub( root, 0 ); 6 } 7 private: 8 int sumSub( TreeNode *node, int num ) { 9 num = 10*num + node->val;10 if( !node->left && !node->right ) { return num; }11 int left = 0, right = 0;12 if( node->left ) { left = sumSub( node->left, num ); }13 if( node->right ) { right = sumSub( node->right, num ); }14 return left + right;15 }16 };
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