Given a String, convert it to K digit integers
Input : test_str = '457336', K = 2
Output : [45, 73, 36]
Explanation : Divided in 2 digit integers.
Input : test_str = '457336', K = 3
Output : [457, 336]
Explanation : Divided in 3 digit integers.
Method #1 : Using int() + slice + loop
In this, we iterate for string and perform slicing till K digits and then perform task of conversion to integer using int().
Python3
# Python3 code to demonstrate working of
# Split Numeric String into K digit integers
# Using int() + slice + loop
# initializing string
test_str = '457336842'
# printing original string
print("The original string is : " + str(test_str))
# initializing substring
K = 3
res = []
for idx in range(0, len(test_str), K):
# converting to int, after slicing
res.append(int(test_str[idx : idx + K]))
# printing result
print("Converted number list : " + str(res))
OutputThe original string is : 457336842
Converted number list : [457, 336, 842]
Time Complexity: O(n), where n is the length of the input list.
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the list “test_list”.
Method #2 : Using list comprehension + int() + slicing
Similar method to above, just a shorthand to solve this problem.
Python3
# Python3 code to demonstrate working of
# Split Numeric String into K digit integers
# Using list comprehension + int() + slicing
# initializing string
test_str = '457336842'
# printing original string
print("The original string is : " + str(test_str))
# initializing substring
K = 3
# one liner to solve problem
res = [int(test_str[idx : idx + K]) for idx in range(0, len(test_str), K)]
# printing result
print("Converted number list : " + str(res))
OutputThe original string is : 457336842
Converted number list : [457, 336, 842]
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #3 : Using regex:
- Import the re module to use regular expressions.
- Define the input string test_str and the number of digits K in each substring.
- Use re.findall() to find all substrings of test_str that contain exactly K digits.
- Use . to match any character, and * to match zero or more occurrences of the preceding character or group.
The pattern .*K matches any K characters. - Use re.findall() to find all substrings in test_str that match the pattern.
- re.findall() returns a list of strings, where each string has K characters.
- Use map() to convert each substring in the resulting list to an integer.
- map() applies the int() function to each element in the list.
- The resulting list contains integers instead of strings.
- Store the resulting list of integers in res.
- Print the list res.
Python3
import re
# Define the input string and the number of digits in each substring
test_str = '457336842'
# printing original string
print("The original string is : " + str(test_str))
K = 3
# Use regular expression to find all K-digit substrings
res = list(map(int, re.findall('.'*K, test_str)))
# printing result
print("Converted number list : " + str(res))
#This code is contributed by Jyothi Pinjala.
OutputThe original string is : 457336842
Converted number list : [457, 336, 842]
The time complexity : O(n/K), where n is the length of the input string test_str. The re.findall() method iterates over the input string in steps of K, and each iteration takes constant time to find the K-character substring. Therefore, the time complexity of re.findall() is O(n/K), and the overall time complexity of the algorithm is also O(n/K).
The auxiliary space :O(n/K) because the resulting list contains n/K elements, each with K digits. The space required to store each element is proportional to K, so the overall space complexity is proportional to n/K * K, which simplifies to O(n/K). Additionally, the re.findall() method may allocate additional memory to store the intermediate results of its search, but this memory usage is also proportional to n/K and is dominated by the space required to store the resulting list.
Method 4: Using recursion
Step-by-step approach
- Define a recursive function split_string that takes a string s and an integer k as arguments.
- The base case of the recursive function is when the input string s is empty. In this case, return an empty list [].
- In the recursive case, split the input string s into a K digit substring and the rest of the string using slicing s[:k] and s[k:], respectively.
- Convert the K digit substring to an integer using int() and append it to the result of the recursive call to split_string() on the rest of the string.
- Call the recursive function split_string with the input string test_str and substring length K as arguments, and store the result in the variable res.
- Print the result of the function using print("Converted number list : " + str(res)).
Python3
# initializing string
test_str = '457336842'
# printing original string
print("The original string is : " + str(test_str))
# initializing substring
K = 3
# defining recursive function to split string
def split_string(s, k):
# base case: if string is empty, return empty list
if not s:
return []
# recursive case: split the string into K digit integers and append to results list
return [int(s[:k])] + split_string(s[k:], k)
# call the recursive function
res = split_string(test_str, K)
# printing result
print("Converted number list : " + str(res))
OutputThe original string is : 457336842
Converted number list : [457, 336, 842]
Time complexity: O(n/K) where n is the length of the input string.
Auxiliary space: O(n/K) in the worst case.
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