Hackerrank - Repeated String

Hackerrank – Problem Statement

A description of the problem can be found on Hackerrank.

Solution

The length of a given word repeated could be too much to be able to calculate the result before the time limit. We need to simplify our solution.

We have a given string – s. Count only "a" characters in the given string – c
Get the length of the result string (given on second line) – n
Find how many times is s in first n characters. – t = n / length(s)
There is a rest of the characters in n-charactede string – rest = n - t * length(s)
Find how many "a"s are in the rest of the string – r.

The result is total number of "a"s:
c * t + r

I created solution in:

Scala
Java
JavaScript
Ruby

All solutions are also available on my GitHub.

Java

import java.util.*;

public class RepeatedString {

    public static void main(String[] args) {
        Scanner stdin = new Scanner(System.in);
        String s = stdin.nextLine();
        long n = Long.parseLong(stdin.nextLine());
        long as = s.chars().filter(c -> c == 'a').count();
        long times = n / s.length();
        long rest = n % s.length();

        long totalAs = times * as
                + s.substring(0, (int) rest).chars().filter(c -> c == 'a').count();
        System.out.println(totalAs);
        stdin.close();
    }
}

import java.util.*;

public class RepeatedString {

public static void main(String[] args) {

Scanner stdin = new Scanner(System.in);

String s = stdin.nextLine();

long n = Long.parseLong(stdin.nextLine());

long as = s.chars().filter(c -> c == 'a').count();

long times = n / s.length();

long rest = n % s.length();

long totalAs = times * as

+ s.substring(0, (int) rest).chars().filter(c -> c == 'a').count();

System.out.println(totalAs);

stdin.close();

}

JavaScript

'use strict';

const processData = input => {
    const lines = input.split('\n');

    const s = lines[0];
    const n = parseInt(lines[1]);
    const as = s.split("").filter(c => c === "a").length;
    const times = parseInt(n / s.length);
    const rest = n % s.length;

    const totalAs = times * as
            + s.slice(0, rest).split("").filter(c => c === "a").length;
    console.log(totalAs);

};

process.stdin.resume();
process.stdin.setEncoding("ascii");

let _input = "";
process.stdin.on("data", input => _input += input);
process.stdin.on("end", () => processData(_input));

'use strict';

const processData = input => {

const lines = input.split('\n');

const s = lines[0];

const n = parseInt(lines[1]);

const as = s.split("").filter(c => c === "a").length;

const times = parseInt(n / s.length);

const rest = n % s.length;

const totalAs = times * as

+ s.slice(0, rest).split("").filter(c => c === "a").length;

console.log(totalAs);

};

process.stdin.resume();

process.stdin.setEncoding("ascii");

let _input = "";

process.stdin.on("data", input => _input += input);

process.stdin.on("end", () => processData(_input));

Scala

import scala.io.Source

object RepeatedString extends App {
  val lines = Source.stdin.getLines().toList
  val string = lines.head
  val letters = lines(1).toLong
  val as = string.count(_ == 'a')
  val times = letters / string.length
  val rest = letters % string.length

  val totalAs = times * as + string.substring(0, rest.toInt).count(_ == 'a')
  println(totalAs)
}

import scala.io.Source

object RepeatedString extends App {

val lines = Source.stdin.getLines().toList

val string = lines.head

val letters = lines(1).toLong

val as = string.count(_ == 'a')

val times = letters / string.length

val rest = letters % string.length

val totalAs = times * as + string.substring(0, rest.toInt).count(_ == 'a')

println(totalAs)

}

Ruby

s = gets.strip
n = gets.strip.to_i

as = s.count("a")
times = n / s.size
rest = n % s.size

totalAs = times * as + s.slice(0, rest).count("a")
puts totalAs

s = gets.strip

n = gets.strip.to_i

as = s.count("a")

times = n / s.size

rest = n % s.size

totalAs = times * as + s.slice(0, rest).count("a")

puts totalAs

Pavol Pidanič

I can count to 1023 with 10 fingers

Hackerrank – Repeated String