blogpost and modification of codes

1 files changed, 38 insertions, 35 deletions

diff --git a/challenge-160/cheok-yin-fung/perl/ch-2.pl b/challenge-160/cheok-yin-fung/perl/ch-2.pl
index d6e71a769a..0c1fb3e121 100644
--- a/challenge-160/cheok-yin-fung/perl/ch-2.pl
+++ b/challenge-160/cheok-yin-fung/perl/ch-2.pl
@@ -1,9 +1,15 @@
 #!/usr/bin/perl
 # The Weekly Challenge 160
 # Task 2 Equilibrium Index
+# Post-Deadline Modification
+# see https://e7-87-83.github.io/coding/challenge_160.html
+# or
+# https://e7-87-83.github.io/code/ch-2-wk160-positive.pl
+# Tuesday, April 19, 2022 AM01:12:42 HKT
+
 use v5.22.0;
 use warnings;
-use List::Util qw/sum/;
+use List::Util qw/sum all/;
 
 
 say ei(@ARGV) if defined($ARGV[0]);
@@ -12,21 +18,26 @@ say ei(@ARGV) if defined($ARGV[0]);
 
 sub ei {
     my @n = @_;
+    my @trial = (undef) x scalar @n;
+    $trial[0] = 1;
+    $trial[$#n] = 1;
     my $ind = int $#n/2;
-    my $previous_ind = $ind;
     my $new_ind = $ind;
     my $hint_lower = sum(@n[0..$ind-1]);
     my $hint_upper = sum(@n[$ind+1..$#n]);
     my $step = 0;
     my $expired_ind = $ind;
-    my $guessed_step = 0;
 
     my $success = $hint_lower == $hint_upper;
     return $ind if $success;
-    
 
     while (!$success) {
-        return -1 if $ind < 1 or $ind > $#n-1;
+        return -1 if all {$_} @trial;
+        $trial[$ind] = 1;
+        # say "LOWER: ", $hint_lower, "; MID: ", 
+        #    $n[$ind], "($ind)", "; UPPER: ",$hint_upper,
+        #    " ;   DIRECTION: ", $step;
+
 
         my $cur_val = $n[$ind];
 
@@ -40,48 +51,40 @@ sub ei {
             $hint_upper = $hint_upper + $n[$expired_ind];
         }
 
+        # Check whether we get an equilibrium index
+        $success = $hint_lower == $hint_upper;
+        return $ind if $success;
 
         # Decide which direction going to move
-        if ($hint_lower+$cur_val < $hint_upper) {
-            $new_ind = $ind+1;
-        }
-        elsif ($hint_lower > $hint_upper+$cur_val) {
-            $new_ind = $ind-1;
-        }
-        elsif ($hint_lower+$cur_val == $hint_upper) {
-            $new_ind = $ind+$step;  # follow the previous direction
-        }
-        elsif ($hint_lower == $hint_upper+$cur_val) {
-            $new_ind = $ind+$step;  # follow the previous direction
-        }
-
-        else {    
-            if ($hint_lower+$cur_val > $hint_upper) {
-                $new_ind = $ind+1;
-            }
-            if ($hint_lower < $hint_upper+$cur_val) {
-                $new_ind = $ind-1;
-            }
-        }    
+        $step = (int rand(2)) % 2 ? +1 : -1;
 
         # Prepare for the next loop block, or, stop
-        $step = $new_ind-$ind;
-        $success = $hint_lower == $hint_upper;
-        return $ind if $success;
-        return -1 if $guessed_step == -$step; # No back and fro!
-        $guessed_step = $step;
+        $new_ind = $ind + $step;
+        if ($new_ind == 0) {
+            $step = +1;
+            $new_ind = 2;
+        }
+        if ($new_ind == $#n) {
+            $step = -1;
+            $new_ind = $#n-2;
+        }
         ($expired_ind, $ind) = ($ind, $new_ind);
     }
 }
 
 
 
-use Test::More tests=>500;
+use Test::More tests=>50;
 say "TESTING:";
 my @n_temp;
-for my $case (1..500) {
-    $n_temp[$_] = 1 + int rand(40) for (0..31);
-    ok ei_simple(@n_temp) == ei(@n_temp);
+for my $case (1..50) {
+    $n_temp[$_] = 20 - int rand(40) for (0..31);
+    my $i = ei(@n_temp);
+    ok (
+           ei_simple(@n_temp) == $i
+                              ||
+        sum(@n_temp[0..$i-1]) == sum(@n_temp[$i+1..$#n_temp])
+    );
 }
 done_testing();