I don't understand why I get MLE on this problem https://codeforces.net/contest/1955/problem/G when using bfs.

Here is the code: https://codeforces.net/contest/1955/submission/255789320.

I was able to solve it later with dfs, but I'm still confused why this bfs that i wrote does not work. Obviously the problem is in this queue Q, but after every bfs call it should be empty again, so size of Q is always <= 100 * 100, which should not get out of memory limit. I would appreciate if someone will help me understand this.