Off-line calculation problem refers to the problem that needs to be calculated by recursive equation. Each line of calculation must be equal to the front, and the result must be behind. You must operate from left to right according to the principle of "multiply first, then divide, then add and subtract", and count the numbers in parentheses, brackets and braces first. Various algorithms can be used to make its calculation simpler and more accurate.

The definition of calculation can be used in many ways, from a fairly precise definition, such as "arithmetic" with various algorithms, to a more abstract definition, such as "calculation of strategy" or "calculation of the success probability of two people in a game".