Peter
Peter Campbell Smith

Find the biggest
and the deepest

Weekly challenge 182 — 12 September 2022

Week 182 - 12 Sep 2022

Task 1

Task — Max index

Write a script to find the index of the first biggest number in the list.

Examples

Example
Input: @n = (5, 2, 9, 1, 7, 6)
Output: 2 (as 3rd element in the list is the biggest number)
Input: @n = (4, 2, 3, 1, 5, 0)
Output: 4 (as 5th element in the list is the biggest number)

Analysis

We are to find the index of the first occurrence of the largest number in @list.

We are going to have to look at every number in the list. It therefore seems best to make a single pass through the list, keeping track of the largest value found so far, and its index. And that's the solution I have submitted.

I thought about solutions involving sorting the list, but that's overkill for such a simple requirement.

Try it 

Try running the script with any input:



example: 1, 2, 3, 4, 5, 4, 3, 2, 1

Script


#!/usr/bin/perl

# Peter Campbell Smith - 2022-09-15
# PWC 182 task 1

use v5.28;
use utf8;
use warnings;

my ($input, @tests, $test, @array, $largest, $position, $j);

@tests = ([5, 2, 9, 1, 7, 6], 
    [4, 2, 3, 1, 5, 0], 
    [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20],
    [-2, -7, -10, -5, -14]);

TEST: for $test (@tests) {
    
    # initialise and show input
    @array = @$test;
    $input = '';
    $input .= qq[$_, ] for @array;
    say qq[\nInput:  (] . substr($input, 0, -2) . ')';
    
    # look for the largest
    $largest = -1e6;
    for $j (0 .. $#array) {
        next if $array[$j] <= $largest;
        $largest = $array[$j];
        $position = $j;
    }
    say qq[Output: $position (largest value = $array[$position])];
}
    

Output


Input:  (5, 2, 9, 1, 7, 6)
Output: 2 (largest value = 9)

Input:  (4, 2, 3, 1, 5, 0)
Output: 4 (largest value = 5)

Input:  (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
Output: 19 (largest value = 20)

Input:  (-2, -7, -10, -5, -14)
Output: 0 (largest value = -2)

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