Question

Implement a StringHash class using python using open addressing and linear probing, it should contain the following methods:

Using strings for the data

1. StringHash(size) — create a new hashTable with a default size of 11 for your array, but allow the user to specify an alternate size if desired

2. addItem(string) — place value into the hashTable iv. bool PindItem(string value) — return true if the value is present, else false

3. findItem(string value) — return true if the value is present, else false

4. removeItem(string) — same as findItem, but it removes the item if present (see the notes on removing from open addressing)

5. displayTable() — returns the complete hash table, one line per element, empty cells as “_empty_”, deleted items as “_deleted_”, and strings as their value

If the array is over 1/2 full, you should create a new larger array and move the old values to the new array using a revised hash method.

Answer 1

class StringHash:
    key = 0
    oldvals = None

    # Define The size and initial values are _empty_
    def __init__(self, size):
        self.size = size
        self.vals = ['_empty_'] * self.size

    # Add value into values if values goes to half it will add new array
    def addItem(self, val):
        if self.vals[self.key] == '_empty_':
            self.vals[self.key] = val
            self.key +=1
            if  self.key >= self.size/2:
                self.size += int(self.size/2)
                self.oldvals = self.vals
                self.vals = ['_empty_'] * self.size
                for i in range(len(self.oldvals)):
                    self.vals[i] = self.oldvals[i]

    # find the value in array
    def findItem(self, val):
        flag = False
        if val in self.vals:
            flag = True
        return flag

    # remove the value in array
    def removeItem(self, val):
        if(self.findItem(val)):
            for i in range(len(self.vals)):
                if self.vals[i] == val:
                    self.vals[i] = '_deleted_'

    # display the value in array
    def displayTable(self):
        for i in range(len(self.vals)):
            print(i,":",self.vals[i])