railroad2

Railroad

ID: railroad2

Difficulty: 1.5

CPU Time: 1 second

Memory: 1024 MB

Solution

For this problem, since the problem is to ensure whether or not there are any "dead-ends", where there is not a matching piece to join a part of a "switch" or "junction" to be part of a loop, there must be a pair for any two "endpoints" of a switch or junction. A junction has 4 endpoints, and a switch has 3, so we can multiply X * 4, and Y * 3, and if these is an even number (modulo divide 2), it is possible.