MathDB

C10

Part of 2021-IMOC

Problems(1)

100x100 grid, spider walking and eating bugs

Source: IMOC 2021 C10

8/12/2021
In a 100100 by 100100 grid, there is a spider and 100100 bugs. Each time, the spider can walk up, down, left or right, and the spider aims to visit all the squares with bugs to eat them all. The spider begins from the top-left corner. Show that no matter where the bugs are, the spider can always eat them all within 20002000 steps.
combinatorics