The input gives you an edge list: dislikes = [[1,2],[1,3],[2,4]] means person dislikes , person dislikes , person dislikes . You need an adjacency list to run BFS. Create graph as an array of empty lists (people are -indexed).
For each pair [a, b], add to graph[a] and to graph[b]. Dislikes are mutual, so edges go both ways. This converts the input into a graph you can traverse.