patternphpMinor

Programming Puzzle - N Teams K Wins each

Submitted by: @import:stackexchange-codereview·Mar 10, 2026·

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eachteamsprogrammingwinspuzzle

Problem

I found a problem here. I am sharing the problem and my attempt at solution. I would like to find out if this is the best approach possible.

One day, at the "Russian Code Cup" event it was decided to play
football as an out of competition event. All participants was divided
into n teams and played several matches, two teams could not play
against each other more than once.

The appointed Judge was the most experienced member - Pavel. But since
he was the wisest of all, he soon got bored of the game and fell
asleep. Waking up, he discovered that the tournament is over and the
teams want to know the results of all the matches.

Pavel didn't want anyone to discover about him sleeping and not
keeping an eye on the results, so he decided to recover the results of
all games. To do this, he asked all the teams and learned that the
real winner was friendship, that is, each team beat the other teams
exactly k times. Help Pavel come up with chronology of the tournir
that meets all the conditions, or otherwise report that there is no
such table.

Input

The first line contains two integers: \$n\$ and \$k\$ (\$1 ≤ n, k ≤ 1000\$).

Output

In the first line print an integer \$m\$ - number of the played
games. The following \$m\$ lines should contain the information about all
the matches, one match per line. The \$i\$-th line should contain two
integers \$ai\$ and \$bi\$ (\$1 ≤ ai\$, \$bi ≤ n\$; \$ai ≠ bi\$). The numbers \$ai\$ and \$bi\$
mean, that in the \$i\$-th match the team with number \$ai\$ won against the
team with number \$bi\$. You can assume, that the teams are numbered from
1 to \$n\$.

If a tournir that meets the conditions of the problem does not exist, then print -1.

My solution:

 ($n * ($n - 1)) / 2) {
    echo "-1\n";exit;
}
$output = $n*$k."\n";
$winMap = array();
for ($i = 1; $i

Solution

Style

You are lacking consistency in the spacing in assignments.

Organisation

It might be worth extracting the algorithm in a function. It makes code easier to read and to test.

 ($n * ($n - 1)) / 2) {
        return "-1\n";
    }
    $output = $n*$k."\n";
    $winMap = array();
    for ($i = 1; $i

Re-using functions

You can use array_fill to write $winMap = array_fill(1, $n, 0);

Code Snippets

<?php
function guessChronology($n, $k)
{
    if ($n * $k > ($n * ($n - 1)) / 2) {
        return "-1\n";
    }
    $output = $n*$k."\n";
    $winMap = array();
    for ($i = 1; $i <= $n; $i++) {
        $winMap[$i] = 0;
    }
    for ($i = 1; $i <= $n; $i++) {
        for ($j = $i + 1; $j <= $n; $j++) {
            if ($winMap[$i] < $k) {
                $output .= "$i $j\n";
                $winMap[$i] += 1;
            } else if ($winMap[$j] < $k) {
                $winMap[$j] += 1;
                $output .=  "$j $i\n";
            }
        }
    }
    return $output;
}

$s = fopen("php://stdin", 'r');
$n = stream_get_contents($s);
$dum = explode(" ",trim($n));
$n = $dum[0];
$k = $dum[1];
echo guessChronology($n, $k);
?>

Context

StackExchange Code Review Q#48738, answer score: 2

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