Leetcode 838. Push Dominoes

Given a line of dominoes where some are initially pushed left (L), right (R), or upright (.), compute the final positions after simultaneous propagation of forces. The core challenge is resolving interactions in segments between fixed pushes (e.g., R...L where forces meet and split, or R...R / L...L that propagate fully), which can be done in linear time by scanning and handling each interval.