What is a hash code? Why are collisions inevitable?

A hash code is a numerical value computed from an object, used for quick search and comparison, for example, in hash tables.

A collision occurs when different objects have the same hash code. Collisions are inevitable because:

• The set of possible objects is usually much larger than the set of possible hash code values (limited size, for example, a 32-bit number).
• According to the "pigeonhole principle" (Dirichlet's principle), with a large number of objects, some will necessarily have the same hash.

Therefore, it is important that the hash function distributes values evenly and minimizes collisions, and that the data structure handles them correctly.