Peak point

You are given an array of altitude gain. Write a script to find the peak point gained.

Examples

Example 1
Input: @gain = (-5, 1, 5, -9, 2)
Output: 1
start: 0
1st change:  0 + (-5) = -5
2nd change: -5 + 1    = -4
3rd change: -4 + 5    = 1
4th change:  1 + (-9) = -8
5th change: -8 + 2    = -6
max(0, -5, -4, 1, -8, -6) = 1

Example 2
Input: @gain = (10, 10, 10, -25)
Output: 30

Example 3
Input: @gain = (3, -4, 2, 5, -6, 1)
Output: 6

Example 4
Input: @gain = (-1, -2, -3, -4)
Output: 0

Example 5
Input: @gain = (-10, 15, 5)
Output: 10

Analysis

This is another task which can probably be reduced to a one-liner, but I have done it more transparently by repeatedly adding (or subtracting) the steps from a starting point of zero.

This is related to the statistical problem known as the drunkard's walk.

Solutions are technically correct, robust and well-engineered. They exemplify a pragmatic approach to problem-solving: prioritizing clarity and guaranteed correctness over premature optimization. The code is modern, idiomatic Perl and is a pleasure to read.

This review may cover either or both challenges for this week.

I am sorry that the 'Try it' feature is currently working very slowly or not at all owing to some issue with my web hosting provider.

Try it 

Try running the script with any input:

Your @steps =

example: 3, 5, 7, -12, 2, 9

⤡

#!/usr/bin/perl

# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge

use v5.26;    # The Weekly Challenge - 2025-09-15
use utf8;     # Week 339 - task 2 - Peak point
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

peak_point(-5, 1, 5, -9, 2);
peak_point(10, 10, 10, -25);
peak_point(3, -4, 2, 5, -6, 1);
peak_point(-1, -2, -3, -4);
peak_point(-10, 15, 5);

my @steps;
push @steps, int(rand(21)) - 10 for 1 .. 100; 
peak_point(@steps);

sub peak_point {
    
    my ($height, $highest, $climb);
    
    # initialise
    $height = 0;
    $highest = 0;
    
    # start climbing
    for $climb (@_) {
        $height += $climb;
        $highest = $height if $height > $highest;
    }
    
    say qq[\nInput:  (] . join(', ', @_) . ')';
    say qq[Output: $highest];
}

9 lines of code

Output from script

Input:  (-5, 1, 5, -9, 2)
Output: 1

Input:  (10, 10, 10, -25)
Output: 30

Input:  (3, -4, 2, 5, -6, 1)
Output: 6

Input:  (-1, -2, -3, -4)
Output: 0

Input:  (-10, 15, 5)
Output: 10

Input:  (7, 10, -5, 6, 8, -7, 5, -7, 1, -3, -10, 2, 2, -4,
   -3, -2, -9, -4, 8, -5, 10, -10, -6, 5, -1, -8, -8, 1,
   -5, -5, -8, -5, -2, 8, -8, -2, -2, 3, -9, -9, -8, -3,
   6, -4, -6, -7, 8, 4, 6, -1, -8, 6, 7, -1, -2, 7, -1, 1,
   -6, -3, 6, -4, -3, -2, -6, -6, 8, 1, -4, 1, -5, 0, 6,
   2, 4, 5, 1, -7, -9, -7, -3, -3, 10, 3, 7, 0, 7, -8, -1,
   -1, 5, -4, -8, 10, -1, -3, -6, 9, -10, 8)
Output: 26