##### Short Problem Definition:

Determine whether given string of parentheses is properly nested.

##### Link

Nesting

##### Complexity:

expected worst-case time complexity is O(N);

expected worst-case space complexity is O(1)

##### Execution:

Because there is only one type of brackets, the problem is easier than Brackets. Just check if there is always a opening bracket before a closing one.

##### Solution:

def solution(S): leftBrackets = 0 for symbol in S: if symbol == '(': leftBrackets += 1 else: if leftBrackets == 0: return 0 leftBrackets -= 1 if leftBrackets != 0: return 0 return 1

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