Parenthesis matching using stack

Parenthesis matching algorithm

PARENTHESIS_MATCHING (EQ, VALID)
This algorithm checks whether the expression EQ written in infix notation is valid or not and assigns TRUE or FALSE to VALID.

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1. Scan EQ from left to right until the end of the equation is encountered:
2.     If”(“is encountered then: put it in the STACK.
3.     If the closing bracket is encountered then:
              (a) If STACK is empty, then Set VALID: = FALSE and return.
              (b) Pop the “(” from the STACK.
        [End of If structure.]
    [End of Step 2 loop.]
4. If STACK is empty, then:
       Set VALID := TRUE
7. Else:
      Set VALID := FALSE

    [End of If structure.]

8. Return

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