Control flow graph & cyclomatic complexity for following procedure

Question

insertion_procedure (int a[], int p [], int N)
{
    int i,j,k;
    for (i=0; i<=N; i++) p[i] = i;
    for (i=2; i<=N; i++)
    {
        k = p[i];
        j = 1;
        while (a[p[j-1]] > a[k]) {p[j] = p[j-1]; j--}
        p[j] = k;
    }
}

I have to find cyclomatic complexity for this code and then suggest some white box test cases and black box test cases. But I am having trouble making a CFG for the code.

Would appreciate some help on test cases as well.

Answer 1

Start by numbering the statements:

 insertion_procedure (int a[], int p [], int N)
 {
(1)    Int i,j,k;
(2)    for ((2a)i=0; (2b)i<=N; (2c)i++) 
(3)        p[i] = i;
(4)    for ((4a)i=2; (4b)i<=N; (4c)i++)
       {
(5)       k=p[i];j=1;
(6)       while (a[p[j-1]] > a[k]) {
(7)           p[j] = p[j-1]; 
(8)           j--
          }
(9)          p[j] = k;
       }

Now you can clearly see which statement executes first and which last etc. so drawing the cfg becomes simple.

Now, to calculate cyclomatic complexity you use one of three methods:

1. Count the number of regions on the graph: 4
2. No. of predicates (red on graph) + 1 : 3 + 1 = 4
3. No of edges - no. of nodes + 2: 14 - 12 + 2 = 4.

Answer 2

The cyclomatic complexity is 4.

1 for the procedure +1 for the for loop +1 for the while loop +1 for the if condition of the while loop.

Answer 3

You can also use McCabe formula M = E-N + 2C
E = edges
N = nodes
C = components
M = cyclomatic complexity

E = 14
N = 12
C = 1

M = 14-12 + 2*1 = 4