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:
- 5 -> 3
- 5 -> 2 -> 1
- -3 -> 11
# Definition for a binary tree node.class TreeNode: def __init__(self, x): self.val = x self.left = None self.right = Noneclass Solution: def pathSum(self, root, sum): """ :type root: TreeNode :type sum: int :rtype: int """ def solve(root,sum): #from root to the child if root is None: return 0 return int(root.val==sum) + solve(root.left,sum-root.val) + solve(root.right,sum-root.val) if root is None: return 0 return solve(root,sum) + self.pathSum(root.left,sum) + self.pathSum(root.right,sum) #choose root and not choose root