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sum-root-to-leaf-numbers.cpp
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// 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.
//
// Note: A leaf is a node with no children.
//
// Example:
//
//
// Input: [1,2,3]
// 1
// / \
// 2 3
// Output: 25
// Explanation:
// The root-to-leaf path 1->2 represents the number 12.
// The root-to-leaf path 1->3 represents the number 13.
// Therefore, sum = 12 + 13 = 25.
//
// Example 2:
//
//
// Input: [4,9,0,5,1]
// 4
// / \
// 9 0
// / \
// 5 1
// Output: 1026
// Explanation:
// The root-to-leaf path 4->9->5 represents the number 495.
// The root-to-leaf path 4->9->1 represents the number 491.
// The root-to-leaf path 4->0 represents the number 40.
// Therefore, sum = 495 + 491 + 40 = 1026.
//
/**
* 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 sum = 0;
int current = 0;
void dfs(TreeNode *root) {
current = current*10 + root->val;
if (!root->left && !root->right) {
sum += current;
current /= 10;
return;
}
if (root->left) {
dfs(root->left);
}
if (root->right) {
dfs(root->right);
}
current /= 10;
}
int sumNumbers(TreeNode* root) {
if (!root) return 0;
dfs(root);
return sum;
}
};