From 61ec2bc8bbe16e41377099a66aeeaab7e35685ab Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Fri, 2 Jun 2023 19:29:52 +0800
Subject: pwc 219

---
 challenge-219/steve-g-lynn/blog.txt      |  1 +
 challenge-219/steve-g-lynn/perl/ch-1.pdl |  7 +++
 challenge-219/steve-g-lynn/perl/ch-2.pl  | 82 ++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 challenge-219/steve-g-lynn/blog.txt
 create mode 100755 challenge-219/steve-g-lynn/perl/ch-1.pdl
 create mode 100755 challenge-219/steve-g-lynn/perl/ch-2.pl

diff --git a/challenge-219/steve-g-lynn/blog.txt b/challenge-219/steve-g-lynn/blog.txt
new file mode 100644
index 0000000000..6df602d517
--- /dev/null
+++ b/challenge-219/steve-g-lynn/blog.txt
@@ -0,0 +1 @@
+https://thiujiac.blogspot.com/2023/06/pwc-219.html
diff --git a/challenge-219/steve-g-lynn/perl/ch-1.pdl b/challenge-219/steve-g-lynn/perl/ch-1.pdl
new file mode 100755
index 0000000000..8984fc03fe
--- /dev/null
+++ b/challenge-219/steve-g-lynn/perl/ch-1.pdl
@@ -0,0 +1,7 @@
+#!/usr/bin/pdl
+
+sub sorted_squares {$list=pdl @_; ($list*$list)->qsort; }
+
+p &sorted_squares(-2,-1,0,3,4); #-- [0 1 4 9 16]
+p &sorted_squares(5,-4,-1,3,6); #-- [1 9 16 25 36]
+
diff --git a/challenge-219/steve-g-lynn/perl/ch-2.pl b/challenge-219/steve-g-lynn/perl/ch-2.pl
new file mode 100755
index 0000000000..b6e80f2598
--- /dev/null
+++ b/challenge-219/steve-g-lynn/perl/ch-2.pl
@@ -0,0 +1,82 @@
+#!/usr/bin/env -S perl -wl
+
+use PDL;
+use PDL::NiceSlice;
+use PDL::AutoLoader;
+
+sub travel_expenditure {
+    my ($ra_costs, $ra_days)=@_;
+    my $costs=pdl $ra_costs;
+    
+    #-- input validation check that costs are reasonable
+    #-- 7 day price is less than 7 * daily price
+    #-- 7 day price is greater than daily price
+ 
+    (scalar(@$ra_costs) == 3) || (die "bad costs");
+    
+    ( ($ra_costs->[1] < (7*$ra_costs->[0]))
+        && ($ra_costs->[1] > $ra_costs->[0]) )
+     || (die "bad costs");  
+
+    #-- 30 day price is less than 30/7* 7-day price
+    #-- 30 day price is greater than 7-day price
+  
+     ( ($ra_costs->[2] < (30/7*$ra_costs->[1]))
+        && ($ra_costs->[2] > $ra_costs->[1]) )
+     || (die "bad costs");  
+  
+    
+    #-- input validation check that dates are in 0 .. 31
+    (((pdl $ra_days)->flat->byte)->max > 31) && (die "bad date");
+    (((pdl $ra_days)->flat->byte)->min < 1) && (die "bad date");
+ 
+ 
+    #-- store days as a 31-element boolean 
+    #-- with 1 at index corresponding to a travel day
+    #-- and 0 at the index for non-travel days   
+    my $days=zeros(31);
+    $days(pdl($ra_days)-1).=1;
+    
+    #-- worth paying for a whole month?
+    #-- check if # of days is greater than 30-day price / 7-day price * 7
+    if ($days->sum > ($ra_costs->[2] / $ra_costs->[1] * 7)) {
+        if ($days(0) & $days(30)) {
+        #if both 1st and last day of 31-day month, then ..
+            return $ra_costs->[2]+$ra_costs->[0];
+            #cost is 30 days price + 1 day price
+        }
+        else {
+            return $ra_costs->[2];
+        }
+    
+    }
+    my $weekly_card=0;
+    my $days_paid_weekly=0;
+    my $weekly_cutoff= int( $ra_costs->[1] / $ra_costs->[0] )+1;
+    
+    #-- cycle through $days looking for clusters of more than
+    #-- 7-day price / 1-day price travel days in a 7-day stretch
+    #-- (weekly cutoff days in a 7-day stretch)
+    
+    my $ctr=0;
+    
+    while ($ctr <= (30 - $weekly_cutoff)) {
+    #-- slow interpreted loop is good enough
+    #-- because the days vector won't scale beyond 31 days
+        my $days_forward = (pdl (6, 30-$ctr) )->min;
+        if ($days($ctr:($ctr+$days_forward))->sum >= $weekly_cutoff) {
+            $weekly_card++;
+            $days_paid_weekly += $days($ctr:($ctr+$days_forward))->sum;
+            $ctr += $days_forward;
+        }
+        else {
+            $ctr += 1;
+        }
+    }
+    return $weekly_card*$costs(1)
+        +( ($days->sum)-$days_paid_weekly ) * $costs(0);
+}
+
+print &travel_expenditure([2,7,25],[2..26,31]); #-- 25
+print &travel_expenditure([2,7,25],[1,5,6,7,9,15]); #-- 11
+print &travel_expenditure([2,7,25],[1..3,5,7,10..12, 14, 20, 30, 31]); #-- 20
-- 
cgit 


From ad4cc0e6599c34423a3aee073741595cbaf8c1eb Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Sat, 3 Jun 2023 11:28:47 +0800
Subject: fix ch-2

---
 challenge-219/steve-g-lynn/perl/ch-2.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/challenge-219/steve-g-lynn/perl/ch-2.pl b/challenge-219/steve-g-lynn/perl/ch-2.pl
index b6e80f2598..fd27d87d8d 100755
--- a/challenge-219/steve-g-lynn/perl/ch-2.pl
+++ b/challenge-219/steve-g-lynn/perl/ch-2.pl
@@ -67,7 +67,7 @@ sub travel_expenditure {
         if ($days($ctr:($ctr+$days_forward))->sum >= $weekly_cutoff) {
             $weekly_card++;
             $days_paid_weekly += $days($ctr:($ctr+$days_forward))->sum;
-            $ctr += $days_forward;
+            $ctr += $days_forward+1;
         }
         else {
             $ctr += 1;
-- 
cgit 


From 96fbd7d14ecb1cb3a3e923fe0ae9007491aad34b Mon Sep 17 00:00:00 2001
From: Stephen Lynn <bizlsg@localhost.localdomain>
Date: Sat, 3 Jun 2023 14:25:57 +0800
Subject: bug fix ch-2.pl

---
 challenge-219/steve-g-lynn/perl/ch-2.pl | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/challenge-219/steve-g-lynn/perl/ch-2.pl b/challenge-219/steve-g-lynn/perl/ch-2.pl
index fd27d87d8d..e138df34e1 100755
--- a/challenge-219/steve-g-lynn/perl/ch-2.pl
+++ b/challenge-219/steve-g-lynn/perl/ch-2.pl
@@ -36,13 +36,16 @@ sub travel_expenditure {
     #-- and 0 at the index for non-travel days   
     my $days=zeros(31);
     $days(pdl($ra_days)-1).=1;
+
     
     #-- worth paying for a whole month?
     #-- check if # of days is greater than 30-day price / 7-day price * 7
+    my $candidates=pdl [Inf, Inf]; #-- candidate solutions
+    
     if ($days->sum > ($ra_costs->[2] / $ra_costs->[1] * 7)) {
         if ($days(0) & $days(30)) {
         #if both 1st and last day of 31-day month, then ..
-            return $ra_costs->[2]+$ra_costs->[0];
+            $candidates(0) .= $ra_costs->[2]+$ra_costs->[0];
             #cost is 30 days price + 1 day price
         }
         else {
@@ -60,9 +63,15 @@ sub travel_expenditure {
     
     my $ctr=0;
     
-    while ($ctr <= (30 - $weekly_cutoff)) {
+    MYLOOP: while ($ctr <= (30 - $weekly_cutoff)) {
     #-- slow interpreted loop is good enough
     #-- because the days vector won't scale beyond 31 days
+
+    #-- start counting 7 days from a travel day only
+        if ($days($ctr)==0){
+            $ctr++;
+            next MYLOOP;
+        } 
         my $days_forward = (pdl (6, 30-$ctr) )->min;
         if ($days($ctr:($ctr+$days_forward))->sum >= $weekly_cutoff) {
             $weekly_card++;
@@ -73,10 +82,12 @@ sub travel_expenditure {
             $ctr += 1;
         }
     }
-    return $weekly_card*$costs(1)
+    $candidates(1) .= $weekly_card*$costs(1)
         +( ($days->sum)-$days_paid_weekly ) * $costs(0);
+    return $candidates->flat->min;
 }
 
+print &travel_expenditure([3.5,7,25],[1..21,25..31]); #-- 28 
 print &travel_expenditure([2,7,25],[2..26,31]); #-- 25
 print &travel_expenditure([2,7,25],[1,5,6,7,9,15]); #-- 11
 print &travel_expenditure([2,7,25],[1..3,5,7,10..12, 14, 20, 30, 31]); #-- 20
-- 
cgit