What methods exist for preventing or resolving collisions in systems or algorithms?

Collisions occur when two different elements receive the same value in a system (for example, the same hash code in a hash table). Various methods are used to prevent or resolve collisions:

1. Collision resolution methods in hash tables:

   • Open addressing: when a collision occurs, the next free cell is searched according to a certain sequence (linear probing, quadratic probing, double hashing).
   • Chaining: each cell stores a linked list of elements with the same hash code.

2. Using high-quality hash functions:

   • A good hash function distributes values evenly, reducing the probability of collisions.

3. In synchronization and distributed systems:

   • Use of unique identifiers (UUID).
   • Application of conflict resolution algorithms (e.g., in databases — locks, transactions).

4. In algorithms and data structures:

   • Using additional checks when keys match.
   • Applying alternative structures (e.g., trees instead of hash tables).

Example of collision resolution with chaining:

class HashTable {
    private LinkedList<Entry>[] table;

    public void put(Key key, Value value) {
        int index = hash(key);
        if (table[index] == null) {
            table[index] = new LinkedList<>();
        }
        // Add or update element in the chain
    }
}

Thus, the choice of method depends on the specific task and requirements for performance and memory.