You're mutating the array in the loop, skipping values, check it here

but saw this in my error report.

See what?

I copied your code and submit it, just got timeout. It means your code is too slow ;-)

I don't know such a way..

Just scroll the page and find red fonts ;-)

To get help, please post your code here and mark it as spoiler. Someone will assist.

Paste your code here using proper markdown and mark your post as having spoiler content.

Is your code returning or printing?