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Two examples of test programs asked during interviews

I include these examples purely for instructional purposes. Generally the subject is given 10 minutes to complete each task.

Please note that if you are ever interviewing with me and you use these for your code examples, I’ll know.

The first problem involves coding the algorythm called "FizzBuzz".

For the numbers from 1 to 100:

If the number is a multiple of 3, output "Fizz".
If it is a multiple of 5, output "Buzz".
If it is a multiple of both, output "FizzBuzz".
Otherwise, output the number.

I offer the following as a good example of how to do this. What I find astounding, is that about 40% of so-called programmers cannot execute this task.

My example not only solves the request, but allows for enhancement capability.


/** 
 * Computes the fizzbuzz for the specified range and returns the text
 *
 * @param   $max    how many terms to return
 * @param   $tests  an array of additional values to check
 * @return  a string of comma separated terms
 */
function fizzBuzz($max=100, $tests=array()) {
    // nomalize maximum value
    $max = $max + 0;
    if ($max < 1) $max = 100;
    
    // set up test values
    $defaultTests = array('Fizz' => 3, 'Buzz' => 5);
    $tests = array_merge($defaultTests, $tests);
    
    $results = '';
    for ($i = 1; $i <= $max; $i++) {
        $result = '';
        
        foreach ($tests as $label => $modulo) if ($i % $modulo == 0) $result .= $label;

        if (!$result) $result = $i;
        
        $results .= $result;
        
        if ($i == $max) {
            $results .= "\n";
        } else {
            $results .= ', ';
        }
    }
    
    return $results."\n";
}

echo '
FizzBuzz: an exercise in silly logic

';
echo fizzBuzz(123, array('Baz' => 47));



This example includes the additional test for multiples of 47

FizzBuzz: an exercise in silly logic

1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz, 11, Fizz, 13, 14, FizzBuzz, 16, 17, Fizz, 19, Buzz, Fizz, 22, 23, Fizz, Buzz, 26, Fizz, 28, 29, FizzBuzz, 31, 32, Fizz, 34, Buzz, Fizz, 37, 38, Fizz, Buzz, 41, Fizz, 43, 44, FizzBuzz, 46, Baz, Fizz, 49, Buzz, Fizz, 52, 53, Fizz, Buzz, 56, Fizz, 58, 59, FizzBuzz, 61, 62, Fizz, 64, Buzz, Fizz, 67, 68, Fizz, Buzz, 71, Fizz, 73, 74, FizzBuzz, 76, 77, Fizz, 79, Buzz, Fizz, 82, 83, Fizz, Buzz, 86, Fizz, 88, 89, FizzBuzz, 91, 92, Fizz, Baz, Buzz, Fizz, 97, 98, Fizz, Buzz, 101, Fizz, 103, 104, FizzBuzz, 106, 107, Fizz, 109, Buzz, Fizz, 112, 113, Fizz, Buzz, 116, Fizz, 118, 119, FizzBuzz, 121, 122, Fizz




Before we move on, one more example.
while($n++<100)echo$n%3?!$$n=$n:Fizz,$n%5?$$n:Buzz,"\n";1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16
17
Fizz
19
Buzz
Fizz
22
23
Fizz
Buzz
26
Fizz
28
29
FizzBuzz
31
32
Fizz
34
Buzz
Fizz
37
38
Fizz
Buzz
41
Fizz
43
44
FizzBuzz
46
47
Fizz
49
Buzz
Fizz
52
53
Fizz
Buzz
56
Fizz
58
59
FizzBuzz
61
62
Fizz
64
Buzz
Fizz
67
68
Fizz
Buzz
71
Fizz
73
74
FizzBuzz
76
77
Fizz
79
Buzz
Fizz
82
83
Fizz
Buzz
86
Fizz
88
89
FizzBuzz
91
92
Fizz
94
Buzz
Fizz
97
98
Fizz
Buzz

Although this code does solve the problem, if anyone ever submits such an example in an interview, I'll walk them out the door.

The second problem involves coding the algorythm for the Fibonacci sequence.

Starting with 1 and 1 as the first two terms, each succesive term is defined as the sum of the previous two.

While this example goes way beyond the original request, it does show how someone could generalize the problem to allow for other sequences of a similar type.


/**
 * Determines a sequence based on the sum of the previous n terms
 *
 * @param   $terms  how many terms to return
 * @param   $prior  the number of terms to sum
 * @param   $seed   the seed value for the first terms
 * @return  a string of comma separated terms
 */
function sumSequence($terms=50, $prior=2, $seed=1) {
    // seed the algorithim with $prior terms of $seed
    $sequence = array($seed);
    $results = $sequence[0];
    for ($p = 1; $p < $prior; $p++) {
        $sequence[$p] = $sequence[0];
        $results .= ', '.$sequence[$p];
    }
    
    for ($i = $prior; $i < $terms; $i++) {
        // next term is sum of the previous n prior elements
        $sequence[$prior] = $sequence[$prior-1];
        for ($p = 2; $p <= $prior; $p++) $sequence[$prior] += $sequence[$prior-$p];
        
        // toss oldest term
        array_shift($sequence);
        
        // output the next term
        $results .= ', '.$sequence[$prior-1];
    }
    
    return $results."\n";
}

function fibonacci($terms) {
    return sumSequence($terms);
}

echo '
Fibonacci: an exercise in recursive logic

';
echo fibonacci(20);

Fibonacci: an exercise in recursive logic

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765