# Sum Root to Leaf Numbers

Source: Internet
Author: User

Given a binary tree containing digits from only 0-9 , 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 represents the number 1->2 12 .
The Root-to-leaf path represents the number 1->3 13 .

Return the sum = + = 25 .

Method of solving problems: Using DFS pre-order traversal

1  Public classSolution {2      Public intsumnumbers (TreeNode root) {3         if(Root = =NULL) {4             return0;5         }6         returnDFS (root, 0);7     }8 9     //The DFS function is a base-based and from the current node to the leaf node. Ten     Private intDFS (TreeNode root,intbase) { One         if(Root = =NULL) { A             return0; -         } -         intsum = base * 10 +Root.val; the         if(Root.left = =NULL&& Root.right = =NULL) { -         returnsum; -         } -         returnDFS (Root.left, sum) +dfs (root.right, sum); +     } -}

Sum Root to Leaf Numbers

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