The Celebrity Problem | GFG | GFG POTD | Java & C++ code | 30-08-2025

In this video, we solve the Celebrity Problem – a popular coding interview question.
A celebrity at a party is defined as someone who is known by everyone but does not know anyone else.

Solution :
Two Pointer : https://github.com/Codefou01/GFG-POTD...

Stack : https://github.com/Codefou01/GFG-POTD...)

We are given an n x n matrix mat[][] where:
mat[i][j] = 1 → person i knows person j
mat[i][j] = 0 → person i does not know person j
mat[i][i] = 1 (self-knowledge is always set)

👉 The task is to find the index of the celebrity, or return -1 if no celebrity exists.

We discuss the optimal O(n) two-pointer approach along with the verification step to ensure correctness.
This problem is commonly asked in interviews and coding platforms like GeeksforGeeks and LeetCode (Find the Celebrity - Problem 277).

✨ Topics Covered:
Problem Explanation with Examples
Naive Approach vs Optimized Approach
Two-Pointer Elimination Method
Time & Space Complexity Analysis


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