Codecademy: A Closure To The Rescue

//sample solution


/* this rotates a string: "lohel".rotate(3) is "hello" */
String.prototype.rotate = function(n) { // n is an integer
    n %= this.length;                   // if n too large: modulo
    var cut = n < 0 ? -n : this.length - n; // cutting point
    return this.substr(cut) + this.substr(0,cut);
};
/*** Wrap everything below this line in a rot13_creator function! ***/

function rot13_creator(){
    // compose the dictionary
    var alph = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    var keys = (alph + alph.toLowerCase()).split("");
    var values = (alph.rotate(13) +
                  alph.rotate(13).toLowerCase()).split("");
    var rot13_dict = {}; // dict: {A:'N', ..., z:'m'}
    keys.forEach( function(key, index){
        rot13_dict[key] = values[index]; } );
    // wrap dictionary in a mapping function
    var rot13_map = function(character) {
        return rot13_dict[character] || character;
    };

    // create the function we're actually interested in
    var rot13 = function(text) {
        return text.split("").map(rot13_map).join("");
    };
 
    return rot13();
}

Sqlcourse Create Table Exercise

Sample solution


create table myemployees_nw0101(
firstname varchar(30),
lastname varchar(30),
title varchar(30),
age number(2),
salary number(10,2)
);

Math Problems: Finding a Product

Script solution for finding a product problem:

Answer: 30

console.log("----------------------------------");

function somfun(a,b,c){

var num = ((a*b)-1)*((b*c)-1)*((c*a)-1);

var den = a*b*c;

if(num % den === 0){

return true;

} else {

return false;

}

}

var max=100;

for(var i=2; i<=max; i++){

for(var j=2; j<=max; j++){

for(var k=2; k<=max; k++){

if(somfun(i,j,k)){

var temp = i*j*k;

console.log(i+" "+j+" "+k+" "+temp);

}

}

}

}

Math Problem: Square Root Sums

Question:

How many pairs of integers (x,y) will satisfy the following equation:
sqrt(x) + sqrt(y) = sqrt(432)

Answer: 13

Solution: Solved using the script below


console.log("----------------------------------");
function comp(a,b){
var temp = Math.sqrt(a)+Math.sqrt(b);
if(temp == Math.sqrt(432)){
return true;
} else {
return false;
}
}
var max=10000;
var count=0;
for(var i=0; i<max; i++){
for(var j=0; j<max; j++){
var temp=comp(i,j);
if(temp){
console.log(i+" "+j);
count++;
}
}
}
console.log("count is " + count);

Math Problem: Cutting a Plane with X Lines

Question: What is the maximum number of regions a plane can be cut into by an X number of lines

Answer: number of regions = 0.5 * ( x^2 + x + 2)

So, for example, if we have 9 lines, the maximum number of regions the plane would be divided into is 46.

Sqlcourse Selecting Data Exercise 6

Problem:

Display all columns for everyone whose first name contains "Mary".

Solution:

select * from empinfo where first like '%Mary%';

Sqlcourse Selecting Data Exercise 5

Problem:

Display all columns for everyone whose first name equals "Mary".

Solution:

select * from empinfo where first = 'Mary';

Sqlcourse Selecting Data Exercise 4

Problem:

Display the first and last names for everyone whose last name ends in an "ay".

Solution:

select first, last from empinfo where last like '%ay';

Sqlcourse Selecting Data Exercise 3

Problem:

Display all columns for everyone that is over 40 years old.

Solution:

select * from empinfo where age > 40;

Sqlcourse Selecting Data Exercise 2

Problem:

Display the first name, last name, and city for everyone that's not from Payson.

Solution:

select first, last, city from empinfo where city <> 'Payson';

Sqlcourse Selecting Data Exercise 1

Problem: 

Display the first name and age for everyone that's in the table.

Solution:

select first, age from empinfo;

Codecademy: Bind It In Chains

// Sample solution

// Paste the rotate function here:
String.prototype.rotate = function(n) { // n is an integer
    n %= this.length; // too large numbers: modulo
    var cut = n < 0 ? -n : this.length - n; // cutting point
    return this.substr(cut) + this.substr(0,cut);
};

var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

var rot13_dict = {};
var newString = alphabet + "" + alphabet.toLowerCase();
var array1 = newString.split("");

var newString2 = alphabet.rotate(13) + "" + alphabet.rotate(13).toLowerCase();
var array2 = newString2.split("");

array1.forEach(function(element, index, array1){
rot13_dict[element]=array2[index];
});
//rot13_dict;
function rot13_map(somechar){
if(alphabet.indexOf(somechar)>=0 || alphabet.toLowerCase().indexOf(somechar)>=0){
return rot13_dict[somechar];
} else {
return somechar;
}
}

//console.log(rot13_map('?'));
//console.log(rot13_map('A'));

function rot13(somestring){
if(somestring.length>1){
return somestring.split("").map(function(n){ return rot13_map(n);}).join("");
} else {
return rot13_map(somestring);
}
}

Codecademy: Wrap It!

// Sample solution

// Paste the rotate function here:
String.prototype.rotate = function(n) { // n is an integer
    n %= this.length; // too large numbers: modulo
    var cut = n < 0 ? -n : this.length - n; // cutting point
    return this.substr(cut) + this.substr(0,cut);
};

var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

var rot13_dict = {};
var newString = alphabet + "" + alphabet.toLowerCase();
var array1 = newString.split("");

var newString2 = alphabet.rotate(13) + "" + alphabet.rotate(13).toLowerCase();
var array2 = newString2.split("");

array1.forEach(function(element, index, array1){
rot13_dict[element]=array2[index];
});
//rot13_dict;
function rot13_map(somechar){
if(alphabet.indexOf(somechar)>=0 || alphabet.toLowerCase().indexOf(somechar)>=0){
return rot13_dict[somechar];
} else {
return somechar;
}
}

console.log(rot13_map('?'));
console.log(rot13_map('A'));

Codecademy: Write A Dictionary

// Sample solution

// Paste the rotate function here:
String.prototype.rotate = function(n) { // n is an integer
    n %= this.length; // too large numbers: modulo
    var cut = n < 0 ? -n : this.length - n; // cutting point
    return this.substr(cut) + this.substr(0,cut);
};

var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

var rot13_dict = {};
var newString = alphabet + "" + alphabet.toLowerCase();
var array1 = newString.split("");

var newString2 = alphabet.rotate(13) + "" + alphabet.rotate(13).toLowerCase();
var array2 = newString2.split("");

array1.forEach(function(element, index, array1){
rot13_dict[element]=array2[index];
});
rot13_dict;

Codecademy: ROT Stands For Rotation

// Sample solution

// Paste the rotate function here:
String.prototype.rotate = function(n) { // n is an integer
    n %= this.length; // too large numbers: modulo
    var cut = n < 0 ? -n : this.length - n; // cutting point
    return this.substr(cut) + this.substr(0,cut);
};

var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

// Now use it:
console.log(alphabet.rotate(13));
console.log(alphabet.rotate(13).rotate(13));

Codecademy: Getting Closer To String Translation

// Sample solution

// This is a dummy, to be refined later
function mapping(character) {
    if (character >= 'A' && character <= 'z') {
        return 'x';
    }
    else return character;
}

function substitute(string) {
    /* your code here */
    return string.split("").map(function(n){ return mapping(n); }).join("");
}

// Test your function:
// this should print   "xxxx xx xxxxxxxxxx!"
console.log(substitute("Make me unreadable!"));

Codecademy: Inline Functions In Chains

// Sample solution

// Sum of squares of negatives, using a loop:
function sum_squares_negatives_loop(array) {
    var sum = 0;
    for (var i = 0; i < array.length; i++) {
        if (array[i] < 0) { // filter: negatives only
            sum += (array[i] * array[i]); // square & add
        }
    }
    return sum;
}

// Same thing without a loop, using Array methods:
function my_sum_squares_neg(array) {
    return array
        .filter( // filter negative numbers:
            function(n) {
                return n<0 ? n : null; // <-- true if and only if n is negative
            }
        )
              // at this point we have an array of negative numbers
        .map( // map each of these numbers to its square
            function(n) {
                return n * n; // <-- the square of n
            }
        )
                 // now, we have an array of squared numbers
        .reduce( // let's add them all together!
            function(sum, next) { // each array element in turn is next
                return sum+=next; // <-- add next (value) to sum
            }, 0 // set sum = 0 initially
        );
}

// test if your function does the same as the loop:
var numbers = [-23, 95, 0, -2, -47];
console.log(sum_squares_negatives_loop(numbers));
console.log(my_sum_squares_neg(numbers));