Bus Routes
Examples
Example 1:
Input: routes = [[1,2,7],[3,6,7]], source = 1, target = 6
Output: 2
Explanation:
Example 2:
Input: routes = [[7,12],[4,5,15],[6],[15,19],[9,12,13]], source = 15, target = 12
Output: -1
Example 3:
Input: routes = [[1,5,7],[3,5,6],[6,8]], source = 5, target = 5
Output: 0
Explanation: