In a binary tree, the sum is a value path

topic

Input a binary tree and an integer, print out all paths in the binary tree where the sum of the node values ​​is the input integer. From the root node of the tree down to the nodes passed by the leaf nodes form a path.

Python problem solving

class TreeNode(object):
    def __init__(self, v=None):
        self.val = v
        self.left = None
        self.right = None


def find_path(root, k):
    res, path = [], []
    cur_sum = 0
    path_in_tree(root, k, cur_sum, path, res)
    return res


def path_in_tree(root, k, cur_sum, path, res):
    if root is None:
        return
    cur_sum += root.val
    path.append(root)
    is_leaf = root.left is None and root.right is None
    if is_leaf and k == cur_sum:
        res.append([v.val for v in path])
    if root.left is not None:
        path_in_tree(root.left, k, cur_sum, path, res)
    if root.right is not None:
        path_in_tree(root.right, k, cur_sum, path, res)
    cur_sum -= root.val
    path.remove(root)


if __name__ == '__main__':
    root = TreeNode(1)
    root.left = TreeNode(3)
    root.right = TreeNode(4)
    root.left.left = TreeNode(5)
    root.right.right = TreeNode(4)
    print find_path(root, 9)