:type sum: int
:rtype: int
"""
path = [0]
ans = [0]
def dfs(node, s):
if not node:
return
s += node.val
for x in path:
if s - x == sum:
ans[0] += 1
path.append(s)
dfs(node.left, s)
dfs(node.right, s)
path.pop()
dfs(root, 0)
return ans[0]
if __name__ == '__main__':
from utils import TreeNode
f = Solution().pathSum
root = TreeNode.make_tree([10, 5, -3, 3, 2, None, 11, 3, -2, None, 1])
assert f(root, 8) == 3
assert f(
TreeNode.make_tree([5, 4, 8, 11, None, 13, 4, 7, 2, None, None, 5, 1]),
22) == 3
