GATE | GATE-CS-2015 (Set 1) | Question 65

Consider the following C program segment.

while (first <= last)
{
   if (array [middle] < search)
      first = middle +1;
   else if (array [middle] == search)
      found = True;
   else last = middle – 1;
   middle = (first + last)/2;
}
if (first < last) not Present = True;

The cyclomatic complexity of the program segment is __________.

(A) 3
(B) 4
(C) 5
(D) 6


Answer: (C)

Explanation: the cyclomatic complexity of a structured program[a] is defined with reference to the control flow graph of the program, a directed graph containing the basic blocks of the program, with an edge between two basic blocks if control may pass from the first to the second. The complexity M is then defined as

    M = E − N + 2P,
where
    E = the number of edges of the graph.
    N = the number of nodes of the graph.
    P = the number of connected components.  

Source: http://en.wikipedia.org/wiki/Cyclomatic_complexity

For a single program (or subroutine or method), P is always equal to 1. So a simpler formula for a single subroutine is

    M = E − N + 2 

For the given program, the control flow graph is:

 E = 13, N = 10.

Therefore, E - N + 2 = 5. 

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