Hash Table Search in Python

Introduction:

This Python code demonstrates the use of a hash table to perform a search for an element using a hash function. A hash table is a data structure that stores key-value pairs and provides fast retrieval of values based on their keys. In this example, we use a simple hash function to map keys to positions in the hash table.

Code:

# Function to check if a key is present in the hash table
def hashFind(key, hashTable):
    if (hashTable[key % 10] == key):  # key is present
        return key % 10 + 1  # return the position
    else:
        return None  # key is not present
# end of function

# Create hashTable with 10 empty positions
hashTable = [None, None, None, None, None, None, None, None, None, None]
print("We have created a hashTable of 10 positions:")
print(hashTable)

# Given list
L = [34, 16, 2, 93, 80, 77, 51]
print("The given list is", L)

# Apply the hash function and populate the hash table
for i in range(0, len(L)):
    hashTable[L[i] % 10] = L[i]

# Print the contents of the hash table
print("The hash table contents are:")
for i in range(0, len(hashTable)):
    print("hashindex=", i, ", value =", hashTable[i])

# Ask the user to enter the number they want to search for
key = int(input("Enter the number to be searched:"))
position = hashFind(key, hashTable)

# Check the result of the hashFind function and print appropriate messages
if position is None:
    print("Number", key, "is not present in the hash table")
else:
    print("Number", key, "present at", position, "position")

Logic:

1. The hashFind function takes a key and a hash table as its parameters.
2. It calculates the hash index for the key using the modulo operation (key % 10) to map the key to a position in the hash table.
3. It then checks if the key at the calculated hash index in the hash table matches the given key.
4. If a match is found, the function returns the position (hash index + 1) of the key in the hash table.
5. If no match is found, the function returns None to indicate that the key is not present in the hash table.
6. The user is prompted to enter a list of numbers, and the hash table is populated using the hash function.
7. The contents of the hash table are printed.
8. The user is asked to enter the number they want to search for.
9. The hashFind function is called to search for the user-provided key in the hash table.
10. The program outputs whether the key is present in the hash table and its position if found.

Output:

>>We have created a hashTable of 10 positions:

>>[None, None, None, None, None, None, None, None, None, None]

>>The given list is [34, 16, 2, 93, 80, 77, 51]

>>The hash table contents are: hashindex= 0 , value = 80

>>hashindex= 1 , value = 51

>>hashindex= 2 , value = 2

>>hashindex= 3 , value = 93

>>hashindex= 4 , value = 34

>>hashindex= 5 , value = 16

>>hashindex= 6 , value = 77

>>hashindex= 7 , value = None

>>hashindex= 8 , value = None

>>hashindex= 9 , value = None

>>Enter the number to be searched: 93

>>Number 93 present at 4 position