Question

给出一个具有整数节点的n元树，如果任何负节点将总和重置为0，如何计算根到叶路径内的最大和。例如，

      -3
    /  |   \
  2    4      1
 / \   |\    / | \
1  -1  1 2  2 -1   3
    |    |     | \
    5   -2     4  7

每个叶到节点路径内的最大和：

{-3，2，1} = 3

{-3，2，-1，5} = 5

{-3，4，1} = 5

{-3，4，2，-2} = 6

{-3，1，2} = 3

{-3，1，-1，4} = 4

{-3，1，-1，7} = 7

{-3，1，3} = 4

路径{-3，1，-1，7} = 7，将是给定条件下的最大总和

Answer 1

import itertools

class Node(object):
    """Basic class to hold node state"""

    def __init__(self, value, children=None):

        self.value = value
        self.children = list() if children is None else children


def dfs(node):
    """Generator that yields the depth-first paths of the tree"""

    path = list()

    def recurse(n):

        path.append(n)

        if not n.children:
            yield path


        for child in n.children:
            for x in recurse(child):
                yield x

        path.pop()

    for v in recurse(node):
        yield path

# Iterate over the tree from the root node
for path in dfs(root):     

    max_path_value = 0
    # Take the path and split it into groups of positive values
    for valid, nodes in itertools.groupby(path, lambda n: n.value >= 0):
        if valid:
            path_value = sum(n.value for n in nodes)
            if path_value > max_path_value:
                max_path_value = path_value

    path_str = ','.join(map(str, [n.value for n in path]))
    print("{}: {}".format(path_str, max_path_value)

在您的树上运行它，给出以下输出，

-3,2,1: 3
-3,2,-1,5: 5
-3,4,1: 5
-3,4,2,-2: 6
-3,1,2: 3
-3,1,-1,4: 4
-3,1,-1,7: 7
-3,1,3: 4

如果负节点重新启动总和从0

1 个答案: