Package g0801_0900.s0815_bus_routes

Class Solution

  • public class Solution
extends Object
    815 - Bus Routes\. Hard You are given an array `routes` representing bus routes where `routes[i]` is a bus route that the ith bus repeats forever. * For example, if `routes[0] = [1, 5, 7]`, this means that the 0th bus travels in the sequence `1 -> 5 -> 7 -> 1 -> 5 -> 7 -> 1 -> ...` forever. You will start at the bus stop `source` (You are not on any bus initially), and you want to go to the bus stop `target`. You can travel between bus stops by buses only. Return _the least number of buses you must take to travel from_ `source` _to_ `target`. Return `-1` if it is not possible. **Example 1:** **Input:** routes = \[\[1,2,7],[3,6,7]], source = 1, target = 6 **Output:** 2 **Explanation:** The best strategy is take the first bus to the bus stop 7, then take the second bus to the bus stop 6. **Example 2:** **Input:** routes = \[\[7,12],[4,5,15],[6],[15,19],[9,12,13]], source = 15, target = 12 **Output:** -1 **Constraints:** * `1 <= routes.length <= 500`. * 1 <= routes[i].length <= 105 * All the values of `routes[i]` are **unique**. * sum(routes[i].length) <= 105 * 0 <= routes[i][j] < 106 * 0 <= source, target < 106

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • numBusesToDestination

        public int numBusesToDestination​(int[][] routes,
                                 int source,
                                 int target)