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  1. Prepare
  2. Data Structures
  3. Stacks
  4. Balanced Brackets

Balanced Brackets

A bracket is considered to be any one of the following characters: (, ), {, }, [, or ].

Two brackets are considered to be a matched pair if the an opening bracket (i.e., (, [, or {) occurs to the left of a closing bracket (i.e., ), ], or }) of the exact same type. There are three types of matched pairs of brackets: [], {}, and ().

A matching pair of brackets is not balanced if the set of brackets it encloses are not matched. For example, {[(])} is not balanced because the contents in between { and } are not balanced. The pair of square brackets encloses a single, unbalanced opening bracket, (, and the pair of parentheses encloses a single, unbalanced closing square bracket, ].

By this logic, we say a sequence of brackets is balanced if the following conditions are met:

  • It contains no unmatched brackets.
  • The subset of brackets enclosed within the confines of a matched pair of brackets is also a matched pair of brackets.

Given strings of brackets, determine whether each sequence of brackets is balanced. If a string is balanced, return YES. Otherwise, return NO.

Function Description

Complete the function isBalanced in the editor below.

isBalanced has the following parameter(s):

  • string s: a string of brackets

Returns

  • string: either YES or NO

Input Format

The first line contains a single integer , the number of strings.
Each of the next lines contains a single string , a sequence of brackets.

Constraints

  • , where is the length of the sequence.
  • All chracters in the sequences ∈ { {, }, (, ), [, ] }.

Output Format

For each string, return YES or NO.

Sample Input

STDIN           Function
-----           --------
3               n = 3
{[()]}          first s = '{[()]}'
{[(])}          second s = '{[(])}'
{{[[(())]]}}    third s ='{{[[(())]]}}'

Sample Output

YES
NO
YES

Explanation

  1. The string {[()]} meets both criteria for being a balanced string.
  2. The string {[(])} is not balanced because the brackets enclosed by the matched pair { and } are not balanced: [(]).
  3. The string {{[[(())]]}} meets both criteria for being a balanced string.