Here is a Python solution for the problem: ```python T = int(input()) for _ in range(T): s

Given a string of characters, find the first repeating character.Input FormatThe first line of input contains T - the number of test cases. It's followed by T lines, each line contains a single string of characters.Output FormatFor each test case, print the first repeating character, separated by a new line. If there are none, print '.'.Constraints1 <= T <= 1000'a' <= str[i] <= 'z'1 <= len(str) <= 104ExampleInput4datastructuresalgorithmssmartinterviewshackerrankOutputa.sa

Question

Given a string of characters, find the first repeating character.Input FormatThe first line of input contains T - the number of test cases. It's followed by T lines, each line contains a single string of characters.Output FormatFor each test case, print the first repeating character, separated by a new line. If there are none, print '.'.Constraints1 <= T <= 1000'a' <= str[i] <= 'z'1 <= len(str) <= 104ExampleInput4datastructuresalgorithmssmartinterviewshackerrankOutputa.sa

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Solution 1

Here is a Python solution for the problem:

T = int(input())
for _ in range(T):
    s

Solution 2

Here is a Python solution for the problem:

def first_repeating_char(s):
    count = {}
    for char in s:
        if char in count:
            return char
        count[char] = 1
    return '.'

T = int(input())
for _ in range(T):
    s = input()
    print(first_repeating_char(s))

This solution works by keeping a count of each character in the string. It iterates over the string from left to right, and for each character, it checks if it has seen the character before. If it has, it returns that character as the first repeating character. If it finishes iterating over the string without finding a repeating character, it returns '.'.

The time complexity of this solution is O(n), where n is the length of the string, because it makes one pass over the string. The space complexity is also O(n), because in the worst case, it needs to store a count for each character in the string.

This problem has been solved

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