Sorting AtCoder ARC 086 C hashes to solve in Ruby, Perl, Java and Python

Introduction

• AtCoder Problems * Use Recommendations to solve past problems. Thanks to AtCoder and AtCoder Problems.

This theme

AtCoder Regular Contest 086 C - Not so Diverse Difficulty: 431

This theme, hash sorting Ruby Speaking of duplicate lists, it's hashes.

ruby.rb

n, k = gets.split.map(&:to_i)
a = gets.split.map(&:to_i)
h = Hash.new(0)
a.each do |x|
  h[x] += 1
end
puts n - h.values.sort.reverse[0, k].inject(:+)

before.rb

h.sort_by{|key, v| -v}.each do |key, v|

after.rb

puts n - h.values.sort.reverse[0, k].inject(:+)

~~ * Ruby * doesn't have a destructive sort of hashes, but it seems to have few uses. ~~ ** Addition ** The original code was to sort the hashes, but in the comments I got the idea of taking the values side as an array, sorting, slicing and summing. Python

python.py

from collections import defaultdict

n, k = map(int, input().split())
a = list(map(int, input().split()))
h = defaultdict(int)
for x in a:
    h[x] += 1
ans = 0
i = 0
for key, v in sorted(h.items(), key=lambda x: -x[1]):
    i += 1
    if i > k:
        ans += v
print(ans)

sort.py

for key, v in sorted(h.items(), key=lambda x: -x[1]):

For * Python *, it's called a dictionary rather than a hash. Also, many players are using Counter instead of defaultdict. Perl

perl.pl

chomp (my ($n, $k) = split / /, <STDIN>);
chomp (my @a = split / /, <STDIN>);
my %h;
$h{$_}++ for @a;
my ($c, $ans) = (0, 0);
for my $v (sort {$b <=> $a} values %h) {
  $c++;
  $ans += $v if $c > $k;
}
print "$ans\n";

sort.pl

for my $v (sort {$b <=> $a} values %h) {

Sorting * Perl * is simple. 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 k = Integer.parseInt(sc.next());
        HashMap<Integer, Integer> h = new HashMap<>();
        for (int i = 0; i < n; i++) {
            int a = Integer.parseInt(sc.next());
            h.merge(a, 1, Integer::sum);
        }
        sc.close();
        List<Integer> s = new ArrayList<>(h.values());
        Collections.sort(s);
        int ans = 0;
        for (int i = s.size() - k - 1; i >= 0; i--) {
            ans += s.get(i);
        }
        System.out.println(ans);
    }
}

sort.java

        List<Integer> s = new ArrayList<>(h.values());
        Collections.sort(s);

For * Java *, it is converted to a list and sorted. ** Addition ** I modified the code from the comments.

Summary

• Solved ARC 086 C
• Become familiar with Ruby
• Become familiar with Python
• Become familiar with Perl
• Become familiar with Java

Referenced site

• Summary of Python sort (list, dictionary type, Series, DataFrame) *