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How to Solve Count the Number of Good Nodes Problem
Master the Count the Number of Good Nodes LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsMedium#3249
LeetCode ProblemCount the Number of Good Nodes
There is an undirected tree with n nodes labeled from 0 to n - 1, and rooted at node 0. You are given a 2D integer array edges of length n - 1, where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. A node is good if all the subtrees rooted at its children have the same size. Return the number of good nodes in the given tree. A subtree of treeName is a tree consisting of a node in treeName and all of its descendants.
TreeDepth-First Search
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Problem Breakdown
Understanding the Count the Number of Good Nodes Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
There is an undirected tree with n nodes labeled from 0 to n - 1, and rooted at node 0. You are given a 2D integer array edges of length n - 1, where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. A node is good if all the subtrees rooted at its children have the same size. Return the number of good nodes in the given tree. A subtree of treeName is a tree consisting of a node in treeName and all of its descendants.
MediumProblem #3249
LeetCodeCount the Number of Good Nodes
Related Topics
TreeDepth-First Search
How Phantom Code Helps
Get real-time assistance for Count the Number of Good Nodes problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[2,6]]
Output
7
# Example 2
Input
edges = [[0,1],[1,2],[2,3],[3,4],[0,5],[1,6],[2,7],[3,8]]
Output
6
# Example 3
Input
edges = [[0,1],[1,2],[1,3],[1,4],[0,5],[5,6],[6,7],[7,8],[0,9],[9,10],[9,12],[10,11]]
Output
12
Constraints
2 <= n <= 105
edges.length == n - 1
edges[i].length == 2
0 <= ai, bi < n
The input is generated such that edges represents a valid tree.
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Solve Count the Number of Good Nodes — There is an undirected tree with n nodes labeled from 0 to n - 1, and rooted at ...
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def solve(input):
# Optimal O(n) solution
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Time: O(n) | Space: O(n)
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Frequently Asked Questions
Common questions about solving Count the Number of Good Nodes and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Count the Number of Good Nodes during interviews?
Phantom Code generates complete solutions instantly with proper complexity analysis, letting you focus on explaining your approach and demonstrating problem-solving skills rather than getting stuck on implementation details during high-pressure situations.
What if the interviewer asks follow-up questions or modifications to problems like Count the Number of Good Nodes?
Phantom Code adapts in real-time. Screenshot the modified problem or use audio mode to capture the interviewer's follow-up, and get an updated solution within seconds — including edge cases and optimizations.
Can Phantom Code help me communicate my solution for problems like Count the Number of Good Nodes?
Yes. Phantom Code provides step-by-step approach explanations with 3 progressive thoughts, so you can walk through your solution naturally. It also provides time and space complexity analysis to discuss trade-offs.
How does Phantom Code assist with different programming languages for Count the Number of Good Nodes type problems?
Phantom Code supports 11 programming languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set your preferred language and get idiomatic solutions.
What coding mistakes does Phantom Code help me avoid during Count the Number of Good Nodes interviews?
Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
Is Phantom Code detectable when solving problems like Count the Number of Good Nodes during live interviews?
No. Phantom Code runs as an invisible desktop overlay that doesn't appear in screen shares, recordings, or proctoring software. It works with Zoom, HackerRank, CodeSignal, CoderPad, and all major platforms.
How does Phantom Code help when I'm struggling with Count the Number of Good Nodes style questions under pressure?
The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
Does Phantom Code work for the coding platforms used in Count the Number of Good Nodes interviews?
Yes. Phantom Code works with all major coding platforms including LeetCode, HackerRank, CodeSignal, CoderPad, HackerEarth, and any browser-based coding environment.
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