let's trace , dislikes = [[1,2],[1,3],[2,4]]. Build graph: , , . Start: color = [-1,-1,-1,-1,-1]. BFS from : color as . Neighbors of : , . Color both as . Neighbors of : (color , opposite, good), (uncolored, color as ).
Neighbors of : (color , opposite, good). Neighbors of : (color , opposite, good). No conflicts. Return true. Group A: {, }. Group B: {, }.