AtCoder Regular Contest C - Make a Rectangle Difficulty: 538
This theme, hash Ruby
ruby.rb
n = gets.to_i
c = gets.split.map(&:to_i)
h = {}
n.times do |i|
if h[c[i]]
h[c[i]] += 1
else
h[c[i]] = 1
end
end
s = h.select{|k, v| v >= 4}.keys.sort{|a, b| b<=>a}
t = h.select{|k, v| v >= 2}.keys.sort{|a, b| b<=>a}
ans = 0
ans = s[0] * s[0] if s.size > 0
ans = [ans, t[0] * t[1]].max if t.size > 1
puts ans
Use the hash to find out the number of occurrences.
In my ring Ruby (2.7.1), the filter method can be used, but in the old environment Ruby (2.3.3) of AtCoder, it becomes ** RE ** </ font>. So I'm using the select method.
Perl
perl.pl
use v5.18; # strict say state
use warnings;
use List::Util qw(max);
chomp (my $n = <STDIN>);
chomp (my @a = split / /, <STDIN>);
my %h;
$h{$_}++ for @a;
my @s = sort {$b <=> $a} grep {$h{$_} >= 4} keys %h;
my @t = sort {$b <=> $a} grep {$h{$_} >= 2} keys %h;
my $ans = 0;
$ans = $s[0] * $s[0] if @s > 0;
$ans = max($ans, $t[0] * $t[1]) if @t > 1;
say $ans;
It uses Perl idioms.
hash.pl
$h{$_}++ for @a;
Java
java.java
import java.util.*;
import java.util.stream.Collectors;
class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = Integer.parseInt(sc.next());
int a[] = new int[n];
for (int i = 0; i < n; i++) {
a[i] = Integer.parseInt(sc.next());
}
sc.close();
Map<Integer, Integer> h = new TreeMap<>(Comparator.reverseOrder());
for (int i = 0; i < n; i++) {
if (h.containsKey(a[i])) {
h.put(a[i], h.get(a[i]) + 1);
} else {
h.put(a[i], 1);
}
}
List<Integer> s = h.entrySet().stream()
.filter(x -> x.getValue() >= 4)
.map(x -> x.getKey())
.collect(Collectors.toList());
List<Integer> t = h.entrySet().stream()
.filter(x -> x.getValue() >= 2)
.map(x -> x.getKey())
.collect(Collectors.toList());
long ans = 0;
if (s.size() > 0) {
ans = (long) s.get(0) * s.get(0);
}
if (t.size() > 1) {
ans = Math.max(ans, (long) t.get(0) * t.get(1));
}
System.out.println(ans);
}
}
I'm using a Java lambda expression. TreeMap is a hash, but Comparator.reverseOrder () can automatically sort the Keys in descending order. It should be converted to long as an integer overflow countermeasure.
| Ruby | Perl | Java | |
|---|---|---|---|
| Code length | 336 Byte | 370 Byte | 1199 Byte |
| Execution time | 140 ms | 135 ms | 664 ms |
| memory | 14988 KB | 28196 KB | 48532 KB |
Referenced site
Recommended Posts