https://acm.timus.ru/problem.aspx?space=1&num=1224&locale=en
Given a matrix of size N, M. (1 <= N, M <= 2 ^ 31 - 1)
Find the number of the turns the robot has to make to visit all the cells in the matrix.
Robot starts at the top leftmost position.
The robot can move in 4 directions: up, down, left, right.
The robot can only move to a cell if it has not visited it before.
The robot can only move to a cell if it is inside the matrix.
Solution
Let’s start with observing a squared matrix of size N x N.
3x4
001
100
101
0 0 1
1 1 0
0 0 0
0 0 0
1 0 1
0 0 0 0 1
1 0 0 0 0
1 0 0 0 1