| 17 October 2025 | Challenge 343 |
Friendly Champions
Task 1: Zero Friend
Submitted by: Mohammad Sajid Anwar
You are given a list of numbers.
Find the number that is closest to zero and return its distance to zero.
Example 1
Input: @nums = (4, 2, -1, 3, -2)
Output: 1
Values closest to 0: -1 and 2 (distance = 1 and 2)
Example 2
Input: @nums = (-5, 5, -3, 3, -1, 1)
Output: 1
Values closest to 0: -1 and 1 (distance = 1)
Example 3
Input: @ums = (7, -3, 0, 2, -8)
Output: 0
Values closest to 0: 0 (distance = 0)
Exact zero wins regardless of other close values.
Example 4
Input: @nums = (-2, -5, -1, -8)
Output: 1
Values closest to 0: -1 and -2 (distance = 1 and 2)
Example 5
Input: @nums = (-2, 2, -4, 4, -1, 1)
Output: 1
Values closest to 0: -1 and 1 (distance = 1)
Solution
We just need to find the element having the smallest absolute value.
use strict;
use warnings;
use List::Util 'min';
sub zero_friend {
min map abs, @_;
}
See the full solution to task 1.
Task 2: Champion Team
Submitted by: Mohammad Sajid Anwar
You have \(n\) teams in a tournament. A matrix grid tells you which team is stronger between any two teams:
If grid[i][j] == 1, then team i is stronger than team j
If grid[i][j] == 0, then team j is stronger than team i
Find the champion team - the one with most wins, or if there is no single such team, the strongest of the teams with most wins. (You may assume that there is a definite answer.)
Example 1
Input: @grid = (
[0, 1, 1],
[0, 0, 1],
[0, 0, 0],
)
Output: Team 0
[0, 1, 1] => Team 0 beats Team 1 and Team 2
[0, 0, 1] => Team 1 beats Team 2
[0, 0, 0] => Team 2 loses to all
Example 2
Input: @grid = (
[0, 1, 0, 0],
[0, 0, 0, 0],
[1, 1, 0, 0],
[1, 1, 1, 0],
)
Output: Team 3
[0, 1, 0, 0] => Team 0 beats only Team 1
[0, 0, 0, 0] => Team 1 loses to all
[1, 1, 0, 0] => Team 2 beats Team 0 and Team 1
[1, 1, 1, 0] => Team 3 beats everyone
Example 3
Input: @grid = (
[0, 1, 0, 1],
[0, 0, 1, 1],
[1, 0, 0, 0],
[0, 0, 1, 0],
)
Output: Team 0
[0, 1, 0, 1] => Team 0 beats teams 1 and 3
[0, 0, 1, 1] => Team 1 beats teams 2 and 3
[1, 0, 0, 0] => Team 2 beats team 0
[0, 0, 1, 0] => Team 3 beats team 2
Of the teams with 2 wins, Team 0 beats team 1.
Example 4
Input: @grid = (
[0, 1, 1],
[0, 0, 0],
[0, 1, 0],
)
Output: Team 0
[0, 1, 1] => Team 0 beats Team 1 and Team 2
[0, 0, 0] => Team 1 loses to Team 2
[0, 1, 0] => Team 2 beats Team 1 but loses to Team 0
Example 5
Input: @grid = (
[0, 0, 0, 0, 0],
[1, 0, 0, 0, 0],
[1, 1, 0, 1, 1],
[1, 1, 0, 0, 0],
[1, 1, 0, 1, 0],
)
Output: Team 2
[0, 0, 0, 0, 0] => Team 0 loses to all
[1, 0, 0, 0, 0] => Team 1 beats only Team 0
[1, 1, 0, 1, 1] => Team 2 beats everyone except self
[1, 1, 0, 0, 0] => Team 3 loses to Team 2
[1, 1, 0, 1, 0] => Team 4 loses to Team 2
Solution
Sorting the teams according to their wins and direct competitions.
We shall interpret a 0 as -1 as the comparison result for direct competitions.
A team compared to itself would give a result of 0, but we won’t ever compare teams to themselves and can safely ignore the values in the matrix’ diagonal.
The last team in the sorted list is the champion.
use strict;
use warnings;
use List::Util 'sum';
sub champion_team {
my @wins = map {sum @$_} @_;
(sort {$wins[$a] <=> $wins[$b] || 2 * $_[$a][$b] - 1} 0 .. $#_)[-1];
}
See the full solution to task 2.
If you have a question about this post or if you like to comment on it, feel free to open an issue in my github repository.