How do I handle input and output?

Modified on Mon, 09 Oct 2023 at 03:17 PM

Your program should always read/write to STDIN/STDOUT. Depending on the programming language, this can be done in multiple ways.

Here follows some examples how to handle input and output in Kattis.

C++

#include <iostream>
#include <algorithm>

int main(void) {
    long long data;
    while (std::cin >> data)
        std::cout << data << std::endl;
    return 0;
}

using System;

public class Program {
    public static void Main() {
        string line;
        while ((line = Console.ReadLine()) != null) {
            Console.WriteLine(line);
        }
    }

Java

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
/* Note that scanner can be very slow on large inputs. Consider using a buffered reader such as the KattIO library if the problem has large inputs*/ 
        while (sc.hasNextLong()) {
            long data = sc.nextLong();
            System.out.println(data);
        }
    }

}

JavaScript on Node.js

const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

rl.on('line', (line) => {
    var data = parseInt(line);
    console.log(data);
});

JavaScript on SpiderMonkey

var line;

while (line = readline()) {
    var data = parseInt(line);
    print(data);
}

PHP

<?php

while (fscanf(STDIN, '%s', $data) === 1) {
    fprintf(STDOUT, "%s\n", $data);
}

Python 3:

#! /usr/bin/python3
import sys
 
for line in sys.stdin:
    data = int(line)
    print(data)