willmadison challenge

20180111.py

s = "abacabaabacaba"

sset = sorted(set(s), key=s.index)
for i in sset:
    count = 0
    for j in s:
        if j == i:
            count += 1
    if count == 1:
        print(i)
        break
else:
    print("_")







# Note: Write a solution that only iterates over the string once and uses O(1) additional memory, since this is what you would be asked to do during a real interview.
#
# Given a string s, find and return the first instance of a non-repeating character in it. If there is no such character, return '_'.
#
# Example
#
#     For s = "abacabad", the output should be
#     firstNotRepeatingCharacter(s) = 'c'.
#
#     There are 2 non-repeating characters in the string: 'c' and 'd'. Return c since it appears in the string first.
#
#     For s = "abacabaabacaba", the output should be
#     firstNotRepeatingCharacter(s) = '_'.
#
#     There are no characters in this string that do not repeat.
#
# Input/Output
#
#     [execution time limit] 4 seconds (go)
#
#     [input] string s
#
#     A string that contains only lowercase English letters.
#
#     Guaranteed constraints:
#     1 ≤ s.length ≤ 105.
#
#     [output] char
#
#     The first non-repeating character in s, or '_' if there are no characters that do not repeat.