Codility : Brackets

A string S consisting of N characters is considered to be properly nestedif 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:

def solution(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 ")".


  • 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):
    # write your code in Python 2.7
    for s in S:
        if s=="[" or s=="(" or s=="{":
        elif not opens:
            return 0

        elif brackets.get(s,False) != opens.pop():
            return 0
    if len(opens) ==0 :
        return 1
    return 0 April 18, 2016, 2:31 a.m.