CS210 - Algorithms and Data Structures I Department of Computer Science National University of Ireland, Maynooth

T Naughton, NUIM
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Laboratory Sheet 4

The stack This lab exam will allow you to increase your understanding of an elementary data structure: the (pushdown) stack. Answer both problems, 4.1 (a straightforward iteration problem) and 4.2 (a stack problem).

Reminder...

• There will no labs for the week beginning 30 October 2000.
• There will be an exam on all material we have done in lectures/labs/tutorials to date during labs of the week beginning 6 November 2000.

Problem 4.1 Write a function that takes an array of characters as a parameter. This array will consist of a sequence of bracket characters, `(' and `)'. Your program must check if the sequence contains the same number of open `(' brackets as close `)' brackets. So, just use a while loop to count the occurances of brackets of each type and print "valid" if they are the same, and "invalid" otherwise. For example, the sequences ")()(" and "(())" are valid, the sequence "(()" is invalid. Your pseudocode should have the following format.

void EqualBrackets(char a[]) {
  /* This function checks if the numbers of occurances of
  ** each bracket type are equal.
  */

  // Your code here
}