Leetcode 777. Swap Adjacent in LR String

Given two strings of 'L', 'R', and 'X', determine if start can be transformed into result by repeatedly applying moves "XL" → "LX" (L moves left) and "RX" → "XR" (R moves right). This reduces to verifying the L/R order (ignoring X) is the same and that every L in start is not left of its target and every R in start is not right of its target.