Count the number of unique characters in a string in Python
Given a string S consisting of lowercase English alphabets, the task is to find the number of unique characters present in the string.
Examples:
Input: S = “geeksforgeeks”
Output: 7
Explanation: The given string “geeksforgeeks” contains 6 unique characters {‘g’, ‘e’, ‘k’, ‘s’, ‘f’, ‘o’, ‘r’}.Input: S = “madam”
Output: 3
Approach: The idea to solve the given problem is to initialize a Set() in python to store all distinct characters of the given string and then, print the size of the set as the required answer.
Below is the implementation of the above approach:
Python3
# Python program for the above approach# Function to count the number of distinct# characters present in the string strdef countDis(str): # Stores all distinct characters s = set(str) # Return the size of the set return len(s)# Driver Codeif __name__ == "__main__": # Given string S S = "geeksforgeeks" print(countDis(S)) |
7
Time Complexity: O(N)
Auxiliary Space: O(1)
Method 2: Using Counter function:
Count the frequencies of all elements using Counter function and number of keys of this frequency dictionary gives the result.
Below is the implementation:
Python3
# Python program for the above approachfrom collections import Counter# Function to count the number of distinct# characters present in the string strdef countDis(str): # Stores all frequencies freq = Counter(str) # Return the size of the freq dictionary return len(freq)# Driver Codeif __name__ == "__main__": # Given string S S = "geeksforgeeks" print(countDis(S)) # This code is contributed by vikkycirus |
Output:
7
Time Complexity: O(N)
Auxiliary Space: O(N)
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