From: Timofei Shatrov There is a theorem by Euler with which you can easily predict if the picture is "drawable". Look. This double house has 4 odd points (it means that odd number of lines goes into it): . . / \7/ \ /___V___\ |\ /|\ /| | X | X | 3|/_\|/_\|3 5 If there is more than 2 odd points the picture is "undrawable" under this rules.
Source: https://ascii.co.uk/art/drawing