Friend HDU-1719 Friend number are defined recursively as follows.
(1) numbers 1 and 2 are friend number;
(2) if a and b are friend numbers, so is ab+a +b;
(3) only the numbers defined in (1
Tag: derivation
Bresenham algorithm derived and application in rpg game
The Bresenham algorithm was originally used to draw straight lines in graphics. No matter how large the screen resolution is, it is always composed of square pixels. When drawing an angled straight