You are given a binary tree in which each node contains an integer value.
Find the number of paths that sum to a given value.
The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).
The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.
Example:
root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8
10
/
5 -3
/
3 2 11
/
3 -2 1
Return 3. The paths that sum to 8 are:
1. 5 -> 3
2. 5 -> 2 -> 1
3. -3 -> 11
1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 int pathSum(TreeNode* root, int sum) { 13 if (!root) return 0; 14 return helper(root, sum) + pathSum(root->left, sum) + pathSum(root->right, sum); 15 } 16 17 int helper(TreeNode* root, int sum) { 18 if (!root) return 0; 19 int count = root->val == sum ? 1 : 0; 20 return count + helper(root->left, sum - root->val) + 21 helper(root->right, sum - root->val); 22 } 23 };