Solving hackerearth problems with Javascript on Windows

HackerEarth is one of the leading coding contest and challenge tools used by some of the major tech giants to recruit talent in India and abroad. HackerEarth provides coding puzzles to programmers that they need to solve in a limited time which can lead to some prizes and/or interviews with an organization. The programming puzzles usually are algorithmic and require reading from standard input (STDIN) and output to standard output. There are several programming languages supported by the HackerEarth platform, Javascript (using NodeJS) being one.

An example problem is like this:

Monk takes a walk:

https://www.hackerearth.com/practice/algorithms/searching/linear-search/practice-problems/algorithm/monk-takes-a-walk/

If you are trying to solve the problems with Javascript (NODE environment), you would select the language of choice - Javascript (NodeJS) - like this:

This will display a basic skeleton program in your code editor:However, if you tried run this code on the Windows command prompt; if will find that you can't end the program as CTRL+D doesn't work on CMD prompt. The problem is, the readline interface provided by Windows itself does not support CTRL+D.

This is one of the ways to solve it,

Replace:

process.stdin.on("end", function () {
   main(stdin_input);
});

With:

process.on("SIGINT", function () {
   main(stdin_input);
   process.exit(0);
});

This will intercept CTRL+C keypress as the key-combination invokes _SIGINT_ event.

THAT'S IT!

Now you can process your input, store it in appropriate data structures and solve the actual problem.

Key things to remember:

1. While processing inputs you need to remember that DOS uses carriage return and line feed ("\r\n") aka CLRF as line ending. So when you finally split std_input to process it, you need to split it based on "\r\n". But when you submit code to HackerEarth, change that back to '\n'.

2. Before submitting the solution to HackerEarth, change process.on("SIGINT",()) code section back to _process.stdin.on("end", ())_

Final Submission:

Keeping these things in mind, the code for given Monk takes a walk problem will be something like this, which will run on the Windows command line with Node JS:

function main(input) {
    var lines = input.split('\r\n');
    var shift = lines.shift();
    lines.pop();
    treeCount(lines);
}

function treeCount(treeLine){
    var d_count=0;
    var temp;
    for(var i=0;i<treeLine.length;i++){
        d_count=0;
        for(var j = 0;j<treeLine[i].length;j++){
        temp = treeLine[i][j].toLowerCase();
        if(temp=='a' || temp=='e' || temp== 'i' || temp== 'o' || temp== 'u')
            d_count++;
        }
        console.log(d_count);
    }
}



process.stdin.resume();
process.stdin.setEncoding("utf-8");
var stdin_input = "";

process.stdin.on("data", function (input) {
    stdin_input += input;
});

process.on("SIGINT", function () {
   main(stdin_input);
   process.exit(0);
});

But when we submit it back to HackerEarth as our solution it will need to be modified like this:

function main(input) {
    var lines = input.split('\n');
    lines.shift();
    //lines.pop();
    treeCount(lines);
}
 
function treeCount(treeLine){
    var d_count=0;
    var temp;
    for(var i=0;i<treeLine.length;i++){
        d_count=0;
        for(var j = 0;j<treeLine[i].length;j++){
        temp = treeLine[i][j].toLowerCase();
        if(temp=='a' || temp=='e' || temp== 'i' || temp== 'o' || temp== 'u')
            d_count++;
        }
        console.log(d_count);
    }
}
 
 
 
process.stdin.resume();
process.stdin.setEncoding("utf-8");
var stdin_input = "";
 
process.stdin.on("data", function (input) {
    stdin_input += input;
});
 
process.stdin.on("end", function () {
   main(stdin_input);
});

TADA! That's it.

Read more...

NodeJS readline interface: NodeJS Readline

Tags

• Programming