Hacker Rank - Algorithms - Diagonal Difference

Hacker Rank - Algorithms - Diagonal Difference

// https://www.hackerrank.com/challenges/diagonal-difference

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

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function main() {
    var n = parseInt(readLine());
    var a = [];
    for(a_i = 0; a_i < n; a_i++){
       a[a_i] = readLine().split(' ');
       a[a_i] = a[a_i].map(Number);
    }

    var convertToFlat = arr => arr.reduce((flatArr, a) => flatArr.concat(a), []);
    
    a = convertToFlat(a);
    var diagonal1 = a.reduce((memo, num, i) => {
        if(Math.floor(i/n) == i%n ) {
            return memo + num;
        } else {
            return memo
        }
    }, 0)
    
    var diagonal2 = a.reduce((memo, num, i) => {
        if(((n-1) - Math.floor(i/n)) == i%n ) {
            return memo + num;
        } else {
            return memo
        }
    }, 0)
    
    console.log(Math.abs(diagonal1 - diagonal2));
}

Hacker Rank - Algorithms - Diagonal Difference - FP

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

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function main() {
    var n = parseInt(readLine());
    var a = [];
    for(a_i = 0; a_i < n; a_i++){
       a[a_i] = readLine().split(' ');
       a[a_i] = a[a_i].map(Number);
    }

    var convertToFlat = arr => arr.reduce((flatArr, a) => flatArr.concat(a), []);
    
    a = convertToFlat(a);
    var diagonal1 = a.filter((num, i) => Math.floor(i/n) == i%n)
                   .reduce((memo, num, i) => memo + num, 0);
    var diagonal2 = a.filter((num, i) => ((n-1) - Math.floor(i/n) == i%n))
                   .reduce((memo, num, i) => memo + num, 0);
    
    console.log(Math.abs(diagonal1 - diagonal2));
}