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LeetCode 2709
You are given an array nums. You can move from i to j if gcd(nums[i], nums[j]) > 1. Check if you can reach any index from any other index.
This is a graph connectivity problem where edges exist between indices with gcd > 1. Use union-find or BFS/DFS.
Key insight: if two numbers share a prime factor, they are connected. Build a graph of prime factors.
