How hard is LeetCode 2378. Choose Edges to Maximize Score in a Tree?

LeetCode 2378. Choose Edges to Maximize Score in a Tree is rated Medium on LeetCode.

What is the time complexity of LeetCode 2378. Choose Edges to Maximize Score in a Tree?

The Python solution on this page runs in O(n).

What is the space complexity of LeetCode 2378. Choose Edges to Maximize Score in a Tree?

The Python solution on this page uses O(n) auxiliary space.

What topics does LeetCode 2378. Choose Edges to Maximize Score in a Tree cover?

LeetCode 2378. Choose Edges to Maximize Score in a Tree is tagged Tree, Depth-First Search and Dynamic Programming on LeetCode.

Is LeetCode 2378. Choose Edges to Maximize Score in a Tree a premium problem?

Yes. LeetCode 2378. Choose Edges to Maximize Score in a Tree is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Choose Edges to Maximize Score in a Tree — LeetCode 2378 Python Solution

MediumLeetCode PremiumTreeDepth-First SearchDynamic Programming

Problem: #2378
Pattern: Tree Traversal
Reading time: 3 min
Source: leetcode.com

The problem

You are given a weighted tree consisting of n nodes numbered from 0 to n - 1. The tree is rooted at node 0 and represented with a 2D array edges of size n where edges[i] = [pari, weighti] indicates that node pari is the parent of node i, and the edge between them has a weight equal to weighti.

Example

Input: edges = [[-1,-1],[0,5],[0,10],[2,6],[2,4]]
Output: 11
Explanation: The above diagram shows the edges that we have to choose colored in red.

Python solution

Python

class Solution:
    def maxScore(self, edges: List[List[int]]) -> int:
        def dfs(i):
            a = b = t = 0
            for j, w in g[i]:
                x, y = dfs(j)
                a += y
                b += y
                t = max(t, x - y + w)
            b += t
            return a, b

        g = defaultdict(list)
        for i, (p, w) in enumerate(edges[1:], 1):
            g[p].append((i, w))
        return dfs(0)[1]

Complexity

Measure	Complexity
Time	O(n)
Space	O(n) auxiliary

Pattern: Tree Traversal

Choose the order — preorder, inorder, postorder, level — and the problem solves itself. LeetCode 2378. Choose Edges to Maximize Score in a Tree is filed here because LeetCode tags it Tree, which is the vocabulary this hub collects.

The tree traversal guide has the Python template for the pattern and the 225 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 2378. Choose Edges to Maximize Score in a Tree?: LeetCode 2378. Choose Edges to Maximize Score in a Tree is rated Medium on LeetCode.
What is the time complexity of LeetCode 2378. Choose Edges to Maximize Score in a Tree?: The Python solution on this page runs in O(n).
What is the space complexity of LeetCode 2378. Choose Edges to Maximize Score in a Tree?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 2378. Choose Edges to Maximize Score in a Tree cover?: LeetCode 2378. Choose Edges to Maximize Score in a Tree is tagged Tree, Depth-First Search and Dynamic Programming on LeetCode.
Is LeetCode 2378. Choose Edges to Maximize Score in a Tree a premium problem?: Yes. LeetCode 2378. Choose Edges to Maximize Score in a Tree is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.