Merge pull request #1398 from phillip-harris/branch-051

Challenge-051 solutions by phillip-harris

1 files changed, 51 insertions, 0 deletions

diff --git a/challenge-051/phillip-harris/perl/ch-1.pl b/challenge-051/phillip-harris/perl/ch-1.pl
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+#!/usr/env/perl
+# Task 1 Challenge 051 Solution by phillip-harris
+# 3 Sum
+# Given an array @Lof integers. Write a script to find all unique
+# triplets such that a + b + c is same as the given target T. Also
+# make sure a <= b <= c.
+# Here is wiki page for more information.
+# Example:
+# @L = (-25, -10, -7, -3, 2, 4, 8, 10);
+# One such triplet for target 0 i.e. -10 + 2 + 8 = 0.
+
+# I read about the "two pointer trick" and decided to try to implement it
+# instead of just brute forcing it.
+
+use strict;
+
+my @L = ( -25, -10, -7, -3, 2, 4, 8, 10 );
+my $target = 0;
+
+@L = sort { $a <=> $b } @L;
+
+print "INPUT:\n";
+print join ",", @L;
+print "\n";
+
+my %triplets;
+
+for ( my $x = 0 ; $x <= $#L ; $x++ ) {
+    my $start   = $x + 1;
+    my $end     = $#L;
+    my $current = $x;
+
+    #print "\n$x\n";
+    while ( ( $end - $start ) > 0 ) {
+        my $result = $L[$current] + $L[$start] + $L[$end];
+
+#print "\n$current $start $end / $L[$current] + $L[$start] + $L[$end] = $result\n";
+        if ( $result == $target ) {
+
+            #print "triplet: $L[$current],$L[$start],$L[$end]\n";
+            $triplets{"$L[$current],$L[$start],$L[$end]"} = 1;
+            $start++;
+            $end--;
+        }
+        elsif ( $result < $target ) { $start++ }
+        else                        { $end-- }
+    }
+}
+
+print "\nOUTPUT:\n";
+print join "\n", keys(%triplets);