Sorting with AlgoBuild. Why do I get an index is out of range error?

Question

I am using AlgoBuild to make a program that sorts numbers.

This is my attempt:

AlgoBuild translates this chart to the following pseudo code:

PROGRAM main
    INPUT int D
    FOR i = 0; i < D; i = i + 1
        INPUT V[i]
    END FOR
    FOR i = 1; i <= D; i = i + 1
        k = i
        FOR j = i + 1; j <= D; j = j + 1
            IF V[k] > V[j]
                k = j
            END IF
        END FOR
        IF i != k
            temp = V[i]
            V[i] = V[k]
            V[k] = temp
        END IF
    END FOR
    FOR i = 0; i < D; i = i + 1
        OUTLN V[i]
    END FOR
END

When running it, I got the following error on the statement IF V[k] > V[j]:

IF ERROR: Array index out of range IN V[k] > V[j]

I didn't expect this error.

I can't understand why it is out of range if I made the assignment k is equal to j. What is my mistake?

Answer 1

Your second and third loop allow their loop variables to become equal to D, but you have not defined V[D], so that will be out of range.

Array indices run from 0 onwards, so if you have D number of values in your array V, the first one is V[0] and the last one is V[D-1], not V[D].

So change <= D in your middle loops to < D, like this:

i = 0; i < D; i = i + 1

and

j = i + 1; j < D; j = j + 1

With those two fixes it works.