Python – Add K between case shifts

Given a string, the task is to add K when a case shift happens.

Input : test_str = ‘GeeKSforGeEKs’, K = ‘*’ 
Output : G*ee*KS*for*G*e*EK*s 
Explanation : After G, lowercase character e is present, * is inserted in between. Same goes for each insertion.

Input : test_str = ‘GeeKS’, K = ‘*’ 
Output : G*ee*KS 
Explanation : Inserted at case toggles, as explained. 

Method #1 : Using loop + isupper() + islower()

In this, we iterate for each element and check at each element if next is of different case, if yes, K is added in junction.

Python3

# Python3 code to demonstrate working of
# Add K between case shifts
# Using loop + isupper() + islower()
import re

# initializing string
test_str = 'GeeKSforGeEKs'

# printing original string
print("The original string is : " + str(test_str))

# initializing K
K = '^'

res = ""
for idx in range(0, len(test_str) - 1):
    # checking for case shift
    if test_str[idx].isupper() and test_str[idx + 1].islower() or test_str[idx].islower() and test_str[idx + 1].isupper():
        res = res + test_str[idx] + K
    else:
        res = res + test_str[idx]
res = res + test_str[-1]

# printing result
print("String after alteration : " + str(res))

Output

The original string is : GeeKSforGeEKs
String after alteration : G^ee^KS^for^G^e^EK^s

Method #2 : Using list comprehension

Another way to solve this problem, just provides shorthand to above method.

Python3

# Python3 code to demonstrate working of
# Add K between case shifts
# Using loop + isupper() + islower()

# initializing string
test_str = 'GeeKSforGeEKs'

# printing original string
print("The original string is : " + str(test_str))

# initializing K
K = '^'

# join() to get result string
res = ''.join([test_str[idx] + K if (test_str[idx].isupper() and test_str[idx + 1].islower()) or
               (test_str[idx].islower() and test_str[idx + 1].isupper()) else test_str[idx] for idx in range(0, len(test_str) - 1)])

res += test_str[-1]

# printing result
print("String after alteration : " + str(res))

Output

The original string is : GeeKSforGeEKs
String after alteration : G^ee^KS^for^G^e^EK^s

The Time and Space Complexity for all the methods are the same:

Time Complexity: O(n)

Space Complexity: O(n)