An efficient solution to HackerRank Repeated String Problem using Python 3.x. The time complexity of the program is O(n). This can also be implemented in Java and C++ as the solution is not Pythonic.

1. Repeated String
Lilah has a string, , of lowercase English letters that she repeated infinitely many times.
Given an integer, , find and print the number of letter a 's in the first letters of Lilah's infinite string.
Input Format
The first line contains a single string, .
The second line contains an integer, .
Constraints
For of the test cases, .
Output Format
Print a single integer denoting the number of letter a 's in the first letters of the infinite string created by
repeating infinitely many times.
Sample Input 0
aba
10
Sample Output 0
7
Explanation 0
The first letters of the infinite string are abaabaabaa . Because there are a 's, we print on a
new line.
Sample Input 1
a
1000000000000
Sample Output 1
1000000000000
Explanation 1
Because all of the first letters of the infinite string are a , we print
on a new line.

2. def​ ​repeatedString​(s, n):
​'''Computes and returns total number of occurrences of the character 'a'
in the prefix of length n of an infinitely repeating string.
Parameters:
s - Input string which is considered to be repeated infinitely.
n - The first number of letters to be considered for counting number
of occurrences of the character 'a' in the infinite string.
Returns:
Total number of occurrences of the character 'a'.
'''
​# Length of string.
len_str = len(s)
​# Number of repeated strings to be considered.
num_strs = n//len_str
​# Remainder: Let's consider an example - s = 'abc' and n = 11.
​# Therefore, the string to be considered for finding the number
​# of occurrences of 'a' will be: 'abcabcabcab'. The string is
​# repeating 3 times(abcabcabc). Now, remaining letters are only 2(ab).
​# Therefore, length of remaining letters is calculated as below syntax.
remainder = n%len_str
​# Counter to count number of a's from given string.
count1 = 0
​# Counter to count a's from the remaining set of letters. In the end, it
​# will be used to calculate total number of a's in the string.
count2 = 0
​for​ i ​in​ range(len_str):
​# Calculating number of occurrences of character 'a' from the given string
​if​ s[i] == ​'a'​:
count1 += 1
​# Calculating number of occurrences from remaining letters
​# if they exist.
​if​ s[i] == ​'a'​ ​and​ i < remainder:
count2 += 1
​# Calculating total number of a's in the string
total = count1*num_strs + count2
​return​ total
# Testing
print(repeatedString(​'aba'​, 10))