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Valid or Well Formed Parentheses | Part - 1

Objective: You have been asked to write an algorithm to find Whether Given the Sequence of parentheses is well-formed. This question was asked in the Amazon Interview.

Input: A String contains a sequence of parentheses

Output: true or false on whether parentheses are well-formed or not


  1. Idea is to have two counters, one for open parentheses '{' and one for close '}'
  2. Read one character at a time and increment one of the counters
  3. If any given point of time count of close parentheses is greater than the open one, return false
  4. If at the end both counters are equal, return true

Example: { { } { } } – Well-formed

{ { } { = Not well-formed



Is {{{{}}}}{}{}{}{}{}{}{}{}{}{}{{{}}} well formed ??? :true
Is {{{{}}}}{}{}{}{{}{}{}{}{}{}{}{{{}}} well formed ??? :false
Is {}{ well formed ??? :false
Is }{ well formed ??? :false
Is {{{{{{{{}}}}}}}} well formed ??? :true

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