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+#!perl
+use strict;
+use warnings FATAL => qw(all);
+
+=prompt
+You are given an array of item prices.
+
+Write a script to find out the final price of each items in the given array.
+
+There is a special discount scheme going on. If there’s an item with a lower or equal price later in the list, you get a discount equal to that later price (the first one you find in order).
+
+Example 1
+
+Input: @prices = (8, 4, 6, 2, 3)
+Output: (4, 2, 4, 2, 3)
+
+Item 0:
+The item price is 8.
+The first time that has price <= current item price is 4.
+Final price = 8 - 4 => 4
+
+Item 1:
+The item price is 4.
+The first time that has price <= current item price is 2.
+Final price = 4 - 2 => 2
+
+Item 2:
+The item price is 6.
+The first time that has price <= current item price is 2.
+Final price = 6 - 2 => 4
+
+Item 3:
+The item price is 2.
+No item has price <= current item price, no discount.
+Final price = 2
+
+Item 4:
+The item price is 3.
+Since it is the last item, so no discount.
+Final price = 3
+
+
+Example 2
+
+Input: @prices = (1, 2, 3, 4, 5)
+Output: (1, 2, 3, 4, 5)
+
+
+Example 3
+
+Input: @prices = (7, 1, 1, 5)
+Output: (6, 0, 1, 5)
+
+Item 0:
+The item price is 7.
+The first time that has price <= current item price is 1.
+Final price = 7 - 1 => 6
+
+Item 1:
+The item price is 1.
+The first time that has price <= current item price is 1.
+Final price = 1 - 1 => 0
+
+Item 2:
+The item price is 1.
+No item has price <= current item price, so no discount.
+Final price = 1
+
+Item 3:
+The item price is 5.
+Since it is the last item, so no discount.
+Final price = 5
+
+=cut
+
+
+
+use List::Util qw(first);
+use Test2::V0 -no_srand => 1;
+
+is(final_price(8, 4, 6, 2, 3), [4, 2, 4, 2, 3], 'Example 1');
+is(final_price(1, 2, 3, 4, 5), [1, 2, 3, 4, 5], 'Example 2');
+is(final_price(7, 1, 1, 5), [6, 0, 1, 5], 'Example 3');
+done_testing();
+
+sub final_price
+{
+     my @arr = @_;
+     my @output;
+
+     for my $idx ( 0 .. $#arr )
+     {
+          my $cand = (first{ $arr[$_] <= $arr[$idx]} $idx + 1 .. $#arr) // $idx;
+          push @output, $idx == $cand ? $arr[$idx] : $arr[$idx] - $arr[$cand];
+     }
+     return [@output];
+}