Accounts Merge Solution

Implementation details:

$1.$ Email ownership: Map each email to the first account that owns it

$2.$ Union on collision: If an email is already owned, union the accounts

$3.$ Collect by root: After all unions, group emails by their root account

$4.$ Sort and format: Each result entry is [name, sorted emails] Edge cases:

• Same name, different people (accounts don't merge unless they share an email)
• Single account (no merging needed)
• All accounts merge into one

Time: $O(nk \cdot \alpha(n))$ for unions where $k$ is average emails per account, plus $O(nk \log(nk))$ for sorting. Space: $O(nk)$ for email map and result.