# A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:
# S is empty;
# S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string; S has the form "VW" where V and W are properly nested strings.
# For example, the string "{[()()]}" is properly nested but "([)()]" is not.
# Write a function:
# int solution(char *S);
# that, given a string S consisting of N characters, returns 1 if S is properly nested and 0 otherwise.
# For example, given S = "{[()()]}", the function should return 1 and given S = "([)()]", the function should return 0, as explained above.
# Assume that:
# N is an integer within the range [0..200,000];
# string S consists only of the following characters: "(", "{", "[", "]", "}" and/or ")". Complexity:
# expected worst-case time complexity is O(N);
# expected worst-case space complexity is O(N) (not counting the storage required for input arguments).

def solution(s):
  sets = dict(zip('({[', ')}]'))
  if(not isinstance(s, str)):
    return "Invalid input"

  collector = []
  for bracket in s:
    if(bracket in sets):
      collector.append(sets[bracket])
    elif bracket not in(sets.values()):
      return "Invalid input"
    elif (bracket != collector.pop()):
      return False
  return not collector


print(solution("()[]{}"))

[]