Optimization problems where the variables are required to take on integer values are called integer programming (IP) problems. If some of the variables are continuous, then we get a mixed variable problem. With all functions as linear, an integer linear programming (ILP) problem is obtained, otherwise it is nonlinear. The ILP problem can be converted to a 0-1 programming problem. Linear problems with discrete variables can also be converted to 0-1 programming problems. Several algorithms are available to solve eg Sysko.