Question

Write a program to find the first non repeating character in a string

Answer 1

We will need a program to return the first element in a string which is repeated just once.

To achieve this, we will be using the following:

(1) List operation

(2) count() function

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count() -

What this function does is it counts the number of times a specific character repeats itself in a string,list,tuple,set.

We will be using this function to see how many times each character in a string repeats and add all the characters to an other list whose count would be 1 and we would be printing the first character of the new list we get.

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PROCESS:

- Create an empty list

- Count the frequency of each element in the string

- Append the elements whose frequency is 1 to the new,empty list

- Print out the first element of the new list, index = 0

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CODE:

String = 'books in a rack'

letters_no_repeat = [x for x in String if String.count(x) == 1 ] #checks for the count of each element and adds the elements of count 1 to a list called letters_no_repeat

print(letters_no_repeat[0]) #prints the first element of the new list

OUTPUT:

b

Answer 2

SOURCE CODE:-

def first_non_repeating_character(str1):

char_order = []

ctr = {}

for c in str1:

if c in ctr:

ctr[c] += 1

else:

ctr[c] = 1 char_order.append(c)

for c in char_order:

if ctr[c] == 1:

return c

return None

print(first_non_repeating_character('abcdef'))

print(first_non_repeating_character('abcabcdef'))

print(first_non_repeating_character('aabbcc'))