Python: Find the first repeated character of a given string where the index of first occurrence is smallest

Last update on April 19 2025 13:06:46 (UTC/GMT +8 hours)

Find repeated character with smallest index.

Write a Python program to find the first repeated character in a given string where the index of the first occurrence is smallest.

Visual Presentation:

Sample Solution:

Python Code:

# Define a function that finds the first repeated character in a string with the smallest distance between the repetitions.
def first_repeated_char_smallest_distance(str1):
    temp = {}  # Create an empty dictionary to store characters and their indices.
    for ch in str1:  # Iterate through each character in the input string.
        if ch in temp:  # If the character is already in the dictionary (repeated),
            return ch, str1.index(ch)  # Return the character and its first occurrence index.
        else:
            temp[ch] = 0  # Add the character to the dictionary with a value of 0 to mark its presence.
    return 'None'  # If no repeated character is found, return 'None'.
# Test the function with different input strings.
print(first_repeated_char_smallest_distance("abcabc"))  # Output: ('a', 0) - 'a' is the first repeated character at index 0.
print(first_repeated_char_smallest_distance("abcb"))    # Output: ('b', 1) - 'b' is the first repeated character at index 1.
print(first_repeated_char_smallest_distance("abcc"))    # Output: ('c', 1) - 'c' is the first repeated character at index 1.
print(first_repeated_char_smallest_distance("abcxxy"))  # Output: ('x', 3) - 'x' is the first repeated character at index 3.

Sample Output:

('a', 0)
('b', 1)
('c', 2)
('x', 3) 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to find the first repeated character based on the smallest first occurrence index using a dictionary.
• Write a Python program to scan a string and return the repeated character whose first occurrence is minimal.
• Write a Python program to use list comprehension and index() to identify the repeated character with the smallest initial index.
• Write a Python program to implement a function that compares indices of first occurrences of repeated characters and returns the one with the lowest index.

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