# Problem Types

The mathematical model of programming problem consists of three elements:

- variables, They are unknown quantities to be determined in the problem and are used to indicate the schemes or measures expressed in quantity in programming, which can be determined and controlled by decision makers;
- Objective function, which is the function of decision variables. Add Max or min to this function according to the optimization objective;
- Constraint conditions. They refer to the restrictions of various resource conditions on the value of decision variables, which are usually expressed as equations or inequalities containing decision variable functions.