Status: IN
Sentinel initial values (-1, 0, None) never collide with valid data because LeetCode's input constraints guarantee the sentinel falls outside the problem's value domain, making sentinel-based boundary elimination unconditionally safe within the stated contract.
Sentinel safety depends on constraints excluding the sentinel value from valid inputs — rook defaulting to (0,0) shows this breaks when the sentinel IS a valid position
Depends on (SL): sentinel-initialization-encodes-boundary-conditions, no-validation-is-deliberate-contract
Unless: rook-position-default-zero