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How to Solve All Ancestors of a Node in a Directed Acyclic Graph Problem
Master the All Ancestors of a Node in a Directed Acyclic Graph LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsMedium#2192
LeetCode ProblemAll Ancestors of a Node in a Directed Acyclic Graph
You are given a positive integer n representing the number of nodes of a Directed Acyclic Graph (DAG). The nodes are numbered from 0 to n - 1 (inclusive). You are also given a 2D integer array edges, where edges[i] = [fromi, toi] denotes that there is a unidirectional edge from fromi to toi in the graph. Return a list answer, where answer[i] is the list of ancestors of the ith node, sorted in ascending order. A node u is an ancestor of another node v if u can reach v via a set of edges.
Depth-First SearchBreadth-First SearchGraphTopological Sort
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Problem Breakdown
Understanding the All Ancestors of a Node in a Directed Acyclic Graph Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given a positive integer n representing the number of nodes of a Directed Acyclic Graph (DAG). The nodes are numbered from 0 to n - 1 (inclusive). You are also given a 2D integer array edges, where edges[i] = [fromi, toi] denotes that there is a unidirectional edge from fromi to toi in the graph. Return a list answer, where answer[i] is the list of ancestors of the ith node, sorted in ascending order. A node u is an ancestor of another node v if u can reach v via a set of edges.
MediumProblem #2192
LeetCodeAll Ancestors of a Node in a Directed Acyclic Graph
Related Topics
Depth-First SearchBreadth-First SearchGraphTopological Sort
How Phantom Code Helps
Get real-time assistance for All Ancestors of a Node in a Directed Acyclic Graph problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
n = 8, edgeList = [[0,3],[0,4],[1,3],[2,4],[2,7],[3,5],[3,6],[3,7],[4,6]]
Output
[[],[],[],[0,1],[0,2],[0,1,3],[0,1,2,3,4],[0,1,2,3]]
# Example 2
Input
n = 5, edgeList = [[0,1],[0,2],[0,3],[0,4],[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
Output
[[],[0],[0,1],[0,1,2],[0,1,2,3]]
Constraints
1 <= n <= 1000
0 <= edges.length <= min(2000, n * (n - 1) / 2)
edges[i].length == 2
0 <= fromi, toi <= n - 1
fromi != toi
There are no duplicate edges.
The graph is directed and acyclic.
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Solve All Ancestors of a Node in a Directed Acyclic Graph — You are given a positive integer n representing the number of nodes of a Directe...
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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 All Ancestors of a Node in a Directed Acyclic Graph and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like All Ancestors of a Node in a Directed Acyclic Graph 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 All Ancestors of a Node in a Directed Acyclic Graph?
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 All Ancestors of a Node in a Directed Acyclic Graph?
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 All Ancestors of a Node in a Directed Acyclic Graph 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 All Ancestors of a Node in a Directed Acyclic Graph 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 All Ancestors of a Node in a Directed Acyclic Graph 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 All Ancestors of a Node in a Directed Acyclic Graph 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 All Ancestors of a Node in a Directed Acyclic Graph 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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