Hi!

I tried to solve this problem using BFS technique, and it seems that my code has passed test cases of huge number of inputs. However, it didn't pass the test case number 12. I don't know what is the fault I fell in it, because I can't trace this test case as it contains huge number of inputs and at the same time not completely shown. If someone can find the logical problem in my code, I hope to tell me what it is.

Problem: https://codeforces.net/problemset/problem/580/C

My solution: https://codeforces.net/contest/580/submission/124986838