How to line split in Kattis problem-solving?

Question

I am currently doing some tests at Kattis and I'm stuck with this one. The code I have written until now gives me the last else statement when console.logging in Visual Studio code. If I type a number below 100 it gives me the first if statement however Kattis only gives me errors. Where does the problem lie here?

I am using JavaScript (Nodejs).

Below is the code I am working on:

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

rl.on('line', (line) => {
    var n = line.split(' ');
    for (var i = 0; i < n.length; i++) {
        var r = parseInt(n[i][0]);
        var e = parseInt(n[i][1]);
        var c = parseInt(n[i][2]);
        if (r > e - c) {
            console.log("do not advertise");
        }
        else if (r < e - c) {
            console.log("advertise");
        } else {
            console.log("does not matter");
        }
    }
});

Nina Scholz · Accepted Answer · 2019-05-06 21:22:34Z

1

You could take a flag for getting the first line and if you got the line number, just split the line for getting the values.

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

var first = true;

rl.on('line', (line) => {
    if (first) {
        n = +line;
        first = false;
        return;
    }
    if (!n || !n--) return; // exit early for not needed lines

    var [r, e, c] = line.split(' ').map(Number); // take numbers

    if (r > e - c) {
        console.log("do not advertise");
    } else if (r < e - c) {
        console.log("advertise");
    } else {
        console.log("does not matter");
    }
});

edited May 6, 2019 at 21:22

answered May 6, 2019 at 21:14

Nina Scholz

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9 Comments

halfer Over a year ago

I'm not up-to-date with my JS, but should the first line have a semicolon line terminator?

Nina Scholz Over a year ago

@halfer, no, please have a look here: What are the rules for JavaScript's automatic semicolon insertion (ASI)?.

halfer Over a year ago

Thanks, I thought that might be the case. I wondered if it could be fixed for the apparent inconsistency though - my OCD set off a big red alarm :-D

Vicky Over a year ago

@NinaScholz Hi Nina! So in this problem I had only one first line which was n.. but if I have two first lines. How would I go about that? open.kattis.com/problems/muddyhike this one is a bit trickier and I am trying a nested for loop but not sure I am doing this correct. const readline = require('readline'); const rl = readline.createInterface({ input: process.stdin, output: process.stdout }) rl.on('line', (line) => { var r, c; for (var i = 0; i < r; i++) { for (var j = 0; j <= c; j++) { console.log([i][j]) } } })

tonythomas01 Over a year ago

@Vicky: I created a gist that would read test cases with internal limits on Node gist.github.com/tonythomas01/9aa6bf46fe0eaaef1d7fb846f8b73ec2

|

ggorlen · Accepted Answer · 2023-02-17 01:15:56Z

Here's a slightly simpler option than the accepted answer using .once("line", ...) to skip the first line:

const readline = require("readline");

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

rl.once("line", line => // collect the first line; in this case, discard it
  rl.on("line", line => { // register another listener to handle the rest
    const [r, e, c] = line.split(/ +/).map(Number);

    if (e - c > r) {
      console.log("advertise");
    }
    else if (e - c < r) {
      console.log("do not advertise");
    }
    else {
      console.log("does not matter");
    }
  })
);

Kattis will automatically send EOF so there's no need to track n.

Promises also work:

const readline = require("readline");

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

rl.once("line", async () => {
  for await (const line of rl) {
    const [r, e, c] = line.split(/ +/).map(Number);

    if (e - c > r) {
      console.log("advertise");
    }
    else if (e - c < r) {
      console.log("do not advertise");
    }
    else {
      console.log("does not matter");
    }
  }
});

See Getting input in Kattis challenges - readline js for help with the general case when you need to colect data from the first line, and/or want to print a single result after all lines have been consumed.

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