Leetcode 1007. Minimum Domino Rotations For Equal Row

Given two equal-length arrays representing the top and bottom numbers of dominoes, find the minimum number of single-domino rotations (swapping top and bottom) needed so that all entries in the top row or all in the bottom row are the same, or return -1 if impossible. The solution hinges on checking candidate target values that must appear on every domino (on at least one side) and counting required swaps.