What problems can arise when multiple threads write to a single array simultaneously?

When multiple threads write to the same array simultaneously, the following issues may occur:

• Race conditions: if two threads try to modify the same element of the array at the same time, the result can be unpredictable.
• Data corruption: without synchronization, the data in the array can become inconsistent.
• Lost updates: one change can overwrite another if operations are not atomic.

To avoid these problems, synchronization mechanisms should be used, such as DispatchQueue with barriers, NSLock, or thread-safe data structures. Atomic operations or copying data for separate thread work can also be applied.