The weekly challenge 325 - Task 2: Final Price

  1 #!/usr/bin/env perl
  2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-325/#TASK2
  3 #
  4 # Task 2: Final Price
  5 # ===================
  6 #
  7 # You are given an array of item prices.
  8 #
  9 # Write a script to find out the final price of each items in the given array.
 10 #
 11 # There is a special discount scheme going on. If there’s an item with a lower
 12 # or equal price later in the list, you get a discount equal to that later
 13 # price (the first one you find in order).
 14 #
 15 ## Example 1
 16 ##
 17 ## Input: @prices = (8, 4, 6, 2, 3)
 18 ## Output: (4, 2, 4, 2, 3)
 19 ##
 20 ## Item 0:
 21 ## The item price is 8.
 22 ## The first time that has price <= current item price is 4.
 23 ## Final price = 8 - 4 => 4
 24 ##
 25 ## Item 1:
 26 ## The item price is 4.
 27 ## The first time that has price <= current item price is 2.
 28 ## Final price = 4 - 2 => 2
 29 ##
 30 ## Item 2:
 31 ## The item price is 6.
 32 ## The first time that has price <= current item price is 2.
 33 ## Final price = 6 - 2 => 4
 34 ##
 35 ## Item 3:
 36 ## The item price is 2.
 37 ## No item has price <= current item price, no discount.
 38 ## Final price = 2
 39 ##
 40 ## Item 4:
 41 ## The item price is 3.
 42 ## Since it is the last item, so no discount.
 43 ## Final price = 3
 44 #
 45 #
 46 ## Example 2
 47 ##
 48 ## Input: @prices = (1, 2, 3, 4, 5)
 49 ## Output: (1, 2, 3, 4, 5)
 50 #
 51 #
 52 ## Example 3
 53 ##
 54 ## Input: @prices = (7, 1, 1, 5)
 55 ## Output: (6, 0, 1, 5)
 56 ##
 57 ## Item 0:
 58 ## The item price is 7.
 59 ## The first time that has price <= current item price is 1.
 60 ## Final price = 7 - 1 => 6
 61 ##
 62 ## Item 1:
 63 ## The item price is 1.
 64 ## The first time that has price <= current item price is 1.
 65 ## Final price = 1 - 1 => 0
 66 ##
 67 ## Item 2:
 68 ## The item price is 1.
 69 ## No item has price <= current item price, so no discount.
 70 ## Final price = 1
 71 ##
 72 ## Item 3:
 73 ## The item price is 5.
 74 ## Since it is the last item, so no discount.
 75 ## Final price = 5
 76 #
 77 ############################################################
 78 ##
 79 ## discussion
 80 ##
 81 ############################################################
 82 #
 83 # We walk from the beginning of @prices to its end. In so doing,
 84 # we check all elements from that element to the end to see if one
 85 # is less than or equal in price. If yes, we calculate the new
 86 # discounted price and stop walking to the end for this iteration.
 87 # Then we check whether there is a discounted price and use either
 88 # that or the original price if there isn't.
 89 
 90 use v5.36;
 91 
 92 final_price(8, 4, 6, 2, 3);
 93 final_price(1, 2, 3, 4, 5);
 94 final_price(7, 1, 1, 5);
 95 
 96 sub final_price( @prices ) {
 97     say "Input: (" . join(", ", @prices) . ")";
 98     my @result = ();
 99     foreach my $i (0..$#prices) {
100         my $discounted = -1;
101         foreach my $j ($i+1..$#prices) {
102             if($prices[$j] <= $prices[$i]) {
103                 $discounted = $prices[$i] - $prices[$j];
104                 last;
105             }
106         }
107         if($discounted >= 0) {
108             push @result, $discounted;
109         } else {
110             push @result, $prices[$i];
111         }
112     }
113     say "Output: (" . join(", ", @result) . ")";
114 }