Creating adjacency list from 2D array of ints - breadth-first-search

Question

I have run in to a roadblock when writing an algorithm to find:
a) the shortest bus route and
b) the route with the least switches.
I need to use BFS to solve it, but we are not given an adjacency list for each vertex, so I am confused as to how to make the adjacency list out of a 2D array of Integers, where each number represents a bus stop, and each row is its own route:
So, [1 2 3 4 5] is Route 1,
[6 7] is Route 2 etc.
Also, the first station of each route is the next station
the bus will reach from the last station of the route,
so each route goes in circles:
1 -> 2 -> 3 -> 4 -> 5 -> 1 -> 2 -> ...
1 2 3 4 5
6 7
8 7 4
2 6
So far what I have is this:
public void fillAdjacencyList(int[][] routes){
for(int i=0; i<routes.length; i++){
for(int j=0; j<routes[i].length; j++){
if(this.stop==routes[i][routes[i].length-1]){
BusStop temp=new BusStop(routes[i][0]);
this.next.add(temp);
}else{
if(routes[i][j]==this.stop){
BusStop temp=new BusStop(routes[i][j+1]);
this.next.add(temp);
}
}
}
}
this.visited='*';
}
The first vertex is initialized when i read the starting point from where I need to find the shortest bus route. Each vertex is defined as:
int stop;
ArrayList<BusStop> next;
char visited;
char created;
int[] line;
public BusStop(int st){
this.stop=st;
this.created='*';
}

Answer 1

The Python function below does the job. I made it in python so it's less verbose and (hopefully) easier to understand
def to_adj(routes):
adj = { }
for route in routes:
for stop in route:
if stop not in adj:
adj[stop] = []
for i in range(len(route)):
adj[route[i]].append(route[(i+1) % len(route)])
return adj