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                             CHALLENGE 078
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Table of Contents
─────────────────

1 Task 1 - Leader Element
.. 1.1 Perl
2 Task 2 - Left Rotation
.. 2.1 Perl





1 Task 1 - Leader Element
═════════════════════════

  You are given an array @A containing distinct integers.

  Write a script to find all leader elements in the array @A. Print (0)
  if none found.

  • An element is leader if it is greater than all the elements to its
    right side.


1.1 Perl
────────

  • Program: [file:perl/ch-1.pl]

  We take input from `@ARGV', loop over it. And then we loop over the
  elements at right, goto next if `$arg' is less than `$elm'. This will
  push all the leader elements to `@leader'.
  ┌────
  │ my @leader;
  │ MAIN: while (my $arg = shift @ARGV) {
  │     foreach my $elm (@ARGV) {
  │         next MAIN if $arg < $elm;
  │     }
  │     push @leader, $arg;
  │ }
  └────


2 Task 2 - Left Rotation
════════════════════════

  You are given array @A containing positive numbers and @B containing
  one or more indices from the array @A.

  Write a script to left rotate @A so that the number at the first index
  of @B becomes the first element in the array. Similary, left rotate @A
  again so that the number at the second index of @B becomes the first
  element in the array.


2.1 Perl
────────

  • Program: [file:perl/ch-2.pl]

  Loop over `@B' & then rotate the elements. Same could've been done
  with Left Rotation, I find this easier to understand.
  ┌────
  │ my @A = qw(10 20 30 40 50);
  │ my @B = qw(3 4);
  │
  │ foreach (@B) {
  │     my @tmp = @A;
  │     foreach (1 ... scalar @tmp - $_) {
  │         unshift @tmp, pop @tmp;
  │     }
  │     print join(', ', @tmp), "\n";
  │ }
  └────