Why do hash table lookups take O ( 1 ) time?

Under the appropriate assumptions on the hash function being used, we can say that hash table lookups take expected O (1) time (assuming you’re using a standard hashing scheme like linear probing or chained hashing). This means that on average, the amount of work that a hash table does to perform a lookup is at most some constant.
For More Information Please Refer:

You May Also Like to Read: