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Task/Sorting-algorithms-Heapsort/Perl-6/sorting-algorithms-heapsort.pl6

@@ -0,0 +1,25 @@
+sub heap_sort ( @list is rw ) {
+    for ( 0 ..^ +@list div 2 ).reverse -> $start {
+        _sift_down $start, @list.end, @list;
+    }
+
+    for ( 1 ..^ +@list ).reverse -> $end {
+        @list[ 0, $end ] .= reverse;
+        _sift_down 0, $end-1, @list;
+    }
+}
+
+sub _sift_down ( $start, $end, @list is rw ) {
+    my $root = $start;
+    while ( my $child = $root * 2 + 1 ) <= $end {
+        $child++ if $child + 1 <= $end and [<] @list[ $child, $child+1 ];
+        return if @list[$root] >= @list[$child];
+        @list[ $root, $child ] .= reverse;
+        $root = $child;
+    }
+}
+
+my @data = 6, 7, 2, 1, 8, 9, 5, 3, 4;
+say 'Input  = ' ~ @data;
+@data.&heap_sort;
+say 'Output = ' ~ @data;