Binary search and selection sort in Perl

biosta · egonSchiele · commit f24b9a6e35b7 · 2018-04-20T08:21:28.000-07:00
* Create 01_binary_search.pl

* Typo fixed in 01_binary_search.pl

* Create 01_selection_sort.pl
diff --git a/01_introduction_to_algorithms/perl5/01_binary_search.pl b/01_introduction_to_algorithms/perl5/01_binary_search.pl
@@ -0,0 +1,43 @@
+sub binary_search {
+
+    my ( $item, @list ) = @_;
+
+    # The borders inside where we are searching in:
+    my $low  = 0;
+    my $high = $#list;
+
+    # Do that until found or until just one element remains:
+    while ( $low <= $high ) {
+
+        # Detect the middle of the array:
+        my $mid = int( ( $low + $high ) / 2 );
+        my $guess = $list[$mid];
+
+        # We found it out:
+        if ( $guess == $item ) {
+            return $mid;
+        }
+
+        # The guess is too high, decrease it:
+        elsif ( $guess > $item ) {
+            $high = --$mid;
+        }
+
+        # The guess is too low, increase it:
+        else {
+            $low = ++$mid;
+        }
+    }
+
+    # Nothing at all found:
+    return 'None';
+
+}
+
+my @my_list = qw /1 3 5 7 9/;
+
+# Should display "1":
+print binary_search( 3, @my_list ), "\n";
+
+# Should display "None":
+print binary_search( -1, @my_list ), "\n";
diff --git a/02_selection_sort/perl5/01_selection_sort.pl b/02_selection_sort/perl5/01_selection_sort.pl
@@ -0,0 +1,32 @@
+# Detect the smallest value in an array
+sub findSmallest {
+
+    my @arr = @_;
+
+    my $smallest       = $arr[0];    # Keep the smallest value
+    my $smallest_index = 0;          # Keep the index of the smallest value
+
+    for ( my $i = 1; $i <= $#arr; $i++ ) {
+        $smallest_index = $i if $arr[$i] < $smallest;
+    }
+
+    return $smallest_index;
+}
+
+# Sort array
+sub selectionSort {
+
+    my @arr = @_;
+
+    my @newArr = ();
+
+    for ( 0 .. $#arr ) {
+        my $smallest_index = findSmallest(@arr);    # Find the smallest element in the array
+        push @newArr, $arr[$smallest_index];        # Add it to the new array
+        splice( @arr, $smallest_index, 1 );         # Delete that element
+    }
+
+    return @newArr;
+}
+
+print join( ' ', selectionSort( 5, 3, 6, 2, 10 ) ), "\n";
