Problem

Given a string, find the first non-repeating character in it. For example, if the input string is "GeeksforGeeks", then the output should be 'f'.
Input:
"GeeksforGeeks"
Output:
'f'

Solution

# Solution:
# The solution below is optimal because it uses a dictionary to store the characters and their counts.
# The dictionary is then iterated over to find the first character with a count of 1.
# The time complexity of this solution is O(n) because the dictionary is iterated over once.
# The space complexity of this solution is O(n) because the dictionary is the same size as the input string.

def first_non_repeating_character(string):
    char_counts = {}
    for char in string:
        if char in char_counts:
            char_counts[char] += 1
        else:
            char_counts[char] = 1
    for char in string:
        if char_counts[char] == 1:
            return char
    return None

print(first_non_repeating_character("GeeksforGeeks"))