HackerRank Python: Merge the Tools! Solution

Table of Contents

Question

Consider the following:

A string, s, of length n where s = c₀c₁. . . . c_n-1.
An integer, k, where k is a factor of n.

We can split s into n/k substrings where each subtring, ti, consists of a contiguous block of k characters in s. Then, use each ti to create string ui such that:

The characters in ui are a subsequence of the characters in ti.
Any repeat occurrence of a character is removed from the string such that each character in ui occurs exactly once. In other words, if the character at some index j in ti occurs at a previous index < j in ti, then do not include the character in string ui.

Given s and k, print n/k lines where each line i denotes string ui. Example s = “AAABCADDE” k = 3 There are three substrings of length 3 to consider: ‘AAA’, ‘BCA’ and ‘DDE’. The first substring is all ‘A’ characters, so u1 = ‘A’. The second substring has all distinct characters, so u2 = ‘BCA’. The third substring has 2 different characters, so u3 = ‘DE’. Note that a subsequence maintains the original order of characters encountered. The order of characters in each subsequence shown is important. Function Description Complete the merge_the_tools function in the editor below. merge_the_tools has the following parameters:

string s: the string to analyze
int k: the size of substrings to analyze

Prints Print each subsequence on a new line. There will be n/k of them. No return value is expected.

Input Format

The first line contains a single string, s. The second line contains an integer, k, the length of each substring.

Constraints

1 <= n <= 10^4, where n is the length of s
1 <= k <= n
It is guaranteed that n is a multiple of k.

Sample Input

STDIN       Function
-----       --------
AABCAAADA   s = 'AABCAAADA'
3           k = 3

Sample Output

AB
CA
AD

Explanation

Split s into n/k = 9/3 = 3 equal parts of length k = 3. Convert each ti to ui by removing any subsequent occurrences of non-distinct characters in ti:

t0 = “AAB” – u0 = “AB”
t1 = “CAA” – u1 = “CA”
t2 = “ADA” – u2 = “AD”

Print each ui on a new line.

Solution

				
					# the complete code as required for hackerrank challenge

def merge_the_tools(string, k):
    split_string=(string[i:i+k] for i in range(0,len(string),k))
    for i in split_string:
        u=[]
        u.append(i[0])
        for j in range(1,len(i)):
            if i[j] in u:
                continue
            else:
                u.append(i[j])

        print(''.join(str(e) for e in u))


if __name__ == '__main__':
    string, k = input(), int(input())
    merge_the_tools(string, k)

Explanation

The merge_the_tools function takes two parameters: string (the input string) and k (the length of each substring).

- split_string is created as a generator expression using a slice operation on string. It splits string into substrings of length k by iterating in steps of k from 0 to the length of string.
- The loop for i in split_string iterates over each substring.
- Inside the loop, an empty list u is initialized to store the unique characters.
- The first character of the current substring i is appended to u using u.append(i[0]).
- Another loop for j in range(1, len(i)) starts from the second character of the current substring and iterates until the end.
- For each character i[j] in the current substring, it checks if it already exists in u. If it does, it continues to the next iteration of the loop. Otherwise, it appends the character to u.
- Finally, print(''.join(str(e) for e in u)) is used to print the resulting subsequence u by joining the characters in u together as a string.