Python – Capitalize repeated characters in a string

• Given an input string with lowercase letters, the task is to write a python program to identify the repeated characters in the string and capitalize them.

Examples:

Input: programming language
Output: pRoGRAMMiNG lANGuAGe
Explanation: r,m,n,a,g are repeated elements

Input: geeks for geeks
Output: GEEKS for GEEKS
Explanation: g,e,k,s are repeated elements

Approach 1:

• We have to keep the character of a string as a key and the frequency of each character of the string as a value in the dictionary.
• Traverse the string and check the frequency of each character using a dictionary if the frequency of the character is greater than one then change the character to the uppercase using the upper() function.

Implementation:

Python3

# function for changing the
# repeated characters to uppercase
def RepeatedUpper(s):

    # declaring dictionary
    dic = {}

    # Traversing the string
    for i in s:

        # If the character is already
        # present in dictionary then increment
        # the frequency of the character
        if i in dic:
            dic[i] = dic[i]+1

   # If the character is not present in
   # the dictionary then inserting
   # the character in the dictionary
        else:
            dic[i] = 1
    ans = ''

    # traversing the string
    for i in s:

        # if the frequency of the character is
        # greater than one
        if dic[i] > 1:

            # change into uppercase
            i = i.upper()

        # appending each character to the ans
        ans = ans+i
    return ans


# Driver code
s = 'geeks for geeks'
# function call
print(RepeatedUpper(s))

Output

GEEKS for GEEKS

Time Complexity: O(n)
Auxiliary Space: O(n)

Approach 2:

Using count() function.If count is greater than 1 then the character is repeated.Later on used upper() to convert to uppercase

Python3

s = "programming language"
new_str=""
for i in s:
    if(i!="" and s.count(i)>1):
        new_str+=i.upper()
    else:
        new_str+=i
print(new_str)

Output

pRoGRAMMiNG lANGuAGe

Time Complexity: O(n²) -> (count function + loop)
Auxiliary Space: O(n)

Approach 3: Using replace() and len() methods

Python3

#Capitalize repeated letters
s = "programming language"
length=len(s)
new_str=""
for i in s:
    x=s.replace(i,"")
    if(len(x)!=length-1):
        new_str+=i.upper()
    else:
        new_str+=i
print(new_str)

Output

pRoGRAMMiNG lANGuAGe

Time Complexity: O(n²) -> (replace function + loop)
Auxiliary Space: O(n)

Approach #4 : Using Counter() function

Python3

from collections import Counter
s = "programming language"
new_str = ""
freq = Counter(s)
for i in s:
    if(i != "" and freq[i] > 1):
        new_str += i.upper()
    else:
        new_str += i
print(new_str)

Output

pRoGRAMMiNG lANGuAGe

Time Complexity: O(n)
Auxiliary Space: O(n)

Approach #5 : Using List Comprehension

In this approach, we first create a Counter object to store the frequency of each character in the string. Then, we use a list comprehension to iterate over the characters in the string, and for each character, we check if its frequency is greater than 1. If it is, we convert it to uppercase using upper(). Finally, we use join() to concatenate the characters and return the result as a single string.

Python3

from collections import Counter

def capitalize_repeated_chars(s):
    freq = Counter(s)
    return "".join([char.upper() if freq[char] > 1 else char for char in s])

s = "programming language"
print(capitalize_repeated_chars(s))

Output

pRoGRAMMiNG lANGuAGe

Time complexity: O(n), where n is the length of the input string.

Auxiliary space: O(n), for storing the frequency of each character in the Counter object.

Approach #6 : Using operator.countOf() method

• In this approach we iterate over the characters in the string. 
• For each character, we check if its frequency(operator.countOf()) is greater than 1. 
• Initialize a new_str with empty string. 
• If it is, we convert it to uppercase using upper() and concatenate to new_str. 
• If not concatenate the character as it is to new_str.
• Finally print the new_str.

Python3

s = "programming language"
new_str=""
import operator
for i in s:
    if(i!="" and operator.countOf(s,i)>1):
        new_str+=i.upper()
    else:
        new_str+=i
print(new_str)

Output

pRoGRAMMiNG lANGuAGe

Time complexity: O(n), where n is the length of the input string.

Auxiliary space: O(n), for storing the frequency of each character.