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How to Solve Number of Equivalent Domino Pairs Problem
Master the Number of Equivalent Domino Pairs LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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LeetCode ProblemNumber of Equivalent Domino Pairs
Given a list of dominoes, dominoes[i] = [a, b] is equivalent to dominoes[j] = [c, d] if and only if either (a == c and b == d), or (a == d and b == c) - that is, one domino can be rotated to be equal to another domino. Return the number of pairs (i, j) for which 0 <= i < j < dominoes.length, and dominoes[i] is equivalent to dominoes[j].
ArrayHash TableCounting
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Problem Breakdown
Understanding the Number of Equivalent Domino Pairs Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
Given a list of dominoes, dominoes[i] = [a, b] is equivalent to dominoes[j] = [c, d] if and only if either (a == c and b == d), or (a == d and b == c) - that is, one domino can be rotated to be equal to another domino. Return the number of pairs (i, j) for which 0 <= i < j < dominoes.length, and dominoes[i] is equivalent to dominoes[j].
EasyProblem #1128
LeetCodeNumber of Equivalent Domino Pairs
Related Topics
ArrayHash TableCounting
How Phantom Code Helps
Get real-time assistance for Number of Equivalent Domino Pairs problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
dominoes = [[1,2],[2,1],[3,4],[5,6]]
Output
1
# Example 2
Input
dominoes = [[1,2],[1,2],[1,1],[1,2],[2,2]]
Output
3
Constraints
1 <= dominoes.length <= 4 * 104
dominoes[i].length == 2
1 <= dominoes[i][j] <= 9
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Solve Number of Equivalent Domino Pairs — Given a list of dominoes, dominoes[i] = [a, b] is equivalent to dominoes[j] = [c...
Here's the optimal approach using Array:
def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
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Frequently Asked Questions
Common questions about solving Number of Equivalent Domino Pairs and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Number of Equivalent Domino Pairs 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 Number of Equivalent Domino Pairs?
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 Number of Equivalent Domino Pairs?
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 Number of Equivalent Domino Pairs 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 Number of Equivalent Domino Pairs 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 Number of Equivalent Domino Pairs 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 Number of Equivalent Domino Pairs 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 Number of Equivalent Domino Pairs 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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