Leetcode 777. Swap Adjacent in LR String - simultaneous linear traversal

A Python "simultaneously linear traversal" solution to Leetcode 777 - Swap Adjacent in LR String. The solution here is the same as the solution to:
Leetcode 2337. Move Pieces to Obtain a String - simultaneously linear traversal
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[Naazneennewreset-hxtj]

while i < n or j < n: in this line
why didn't we use and operator instead of using or operator and then later breaking if i==n or j==n ?
can anyone please clarify this to me cause am stuck here