At first seeing question i just got into using bfs on matrix to get minimum distance if possible but cant get to solution with it. can it be done with bfs?? here is link for question- https://codeforces.net/contest/1721/problem/B

I want to code A. Get together with approach by limiting value of f(t) ? but i cant get through it ? can i use sweep line algorithm.... after limiting value?and how to code it?here is link to question https://codeforces.net/edu/course/2/lesson/6/3/practice/contest/285083/problem/A