Discrete mathematics is difficult. The research object of discrete mathematics is more abstract and theoretical than high number, which mainly involves set theory, graph theory, mathematical logic and so on. It needs more thinking and logical reasoning ability, and high numbers involve the calculation and application of calculus, linear algebra and differential equations. Compared with high numbers, many concepts and terms in discrete mathematics, including cartesian products in set theory, nodes in graph theory and propositions in mathematical logic, need to spend more time and energy to understand and remember, while high numbers mainly focus on derivatives, integrals and solutions in differential equations in calculus. So discrete mathematics is very difficult.