Programming Challenges

[Pho3nix]

Hi,

So I'm looking for some practice stuff to learn new concepts and expand my horizons.
Was using this : https://www.reddit.com/r/dailyprogrammer

But the challenges for this week are a little out there :wtf:

Any sites you can recommend on challenges to test your know how?
The whole, look at a problem you have and solve it isn't working because I'm kinda perfect

 

[Ho3n3r]

https://projecteuler.net/archives

 

[jonno_081]

https://leetcode.com/ => its a bit addictive...

 

[Pho3nix]

https://leetcode.com/ => its a bit addictive...

OMG this is addictive and so furking annoying at the same time.
I like it

 

[Pho3nix]

https://projecteuler.net/archives

Can't access from here, will try from home.

 

[mr_norris]

Entelect Challenge?

Learn some stuff and possibly win money

 

[[)roi(]]

http://programmers.stackexchange.co...can-i-find-programming-puzzles-and-challenges

 

[krycor]

http://www.pythonchallenge.com/

 

[HibiscusTunes]

http://codingame.com/ and https://www.hackerrank.com/ and https://www.codechef.com/
The first one is quite fun

 

[HibiscusTunes]

http://www.pythonchallenge.com/

Nice

 

[Batista]

http://codingame.com/ and https://www.hackerrank.com/ and https://www.codechef.com/
The first one is quite fun

Wow really impressed with codingame!!

 

[Solarion]

https://www.testdome.com/Programming-Tests/

 

[Solarion]

One I had for an interview some time back.

Question:

Write a function that checks if a given sentence is a palindrome. A palindrome is a word, phrase, verse, or sentence that reads the same backward or forward. Only the order of English alphabet letters (A-Z and a-z) should be considered, other characters should be ignored.

For example, IsPalindrome("Noel sees Leon.") should return true as spaces, period, and case should be ignored resulting with "noelseesleon" which is a palindrome since it reads same backward and forward.

My Answer:

using System;

public class Palindrome
    {
        public static bool IsPalindrome(string str)
        {

            int min = 0;
            int max = str.Length - 1;
            while (true)
            {
                if (min > max)
                {
                    return true;
                }
                char a = str[min];
                char b = str[max];

                // Scan forward for a while invalid.
                while (!char.IsLetterOrDigit(a))
                {
                    min++;
                    if (min > max)
                    {
                        return true;
                    }
                    a = str[min];
                }

                // Scan backward for b while invalid.
                while (!char.IsLetterOrDigit(b))
                {
                    max--;
                    if (min > max)
                    {
                        return true;
                    }
                    b = str[max];
                }

                if (char.ToLower(a) != char.ToLower(b))
                {
                    return false;
                }
                min++;
                max--;
            }



            throw new NotImplementedException("Waiting to be implemented.");
        }

        public static void Main(string[] args)
        {
            Console.WriteLine(IsPalindrome("Noel sees Leon."));
            Console.ReadLine(); 
        }
    }

 

[[)roi(]]

One I had for an interview some time back.

Cool, but you could have also done it with an array: ToCharArray() and Linq (Select & Where)

Here e.g. is the same in Swift; using an array and higher order functions (i.e. similar concept to Linq).

extension String
{
  func isPalindrome() -> Bool {
    let lower = self.lowercaseString.unicodeScalars.filter
      { 97...122 ~= Int($0.value) }.map { String($0) }.joinWithSeparator("")
    return lower == String(lower.characters.reverse())
  }
}

"Noel sees Leon.".isPalindrome() // true

C# Linq version example, hopefully code correct; didn't bother to run it through VS.

public static bool IsPalindrome(string str)
{
   var onlyLetters = str.ToLower().Where(c => Char.IsLetter(c)).ToArray();
   return new String(onlyLetters) == new String(onlyLetters.Reverse());
}

 

[Pho3nix]

One I had for an interview some time back.

Question:



My Answer:

using System;

public class Palindrome
    {
        public static bool IsPalindrome(string str)
        {

            int min = 0;
            int max = str.Length - 1;
            while (true)
            {
                if (min > max)
                {
                    return true;
                }
                char a = str[min];
                char b = str[max];

                // Scan forward for a while invalid.
                while (!char.IsLetterOrDigit(a))
                {
                    min++;
                    if (min > max)
                    {
                        return true;
                    }
                    a = str[min];
                }

                // Scan backward for b while invalid.
                while (!char.IsLetterOrDigit(b))
                {
                    max--;
                    if (min > max)
                    {
                        return true;
                    }
                    b = str[max];
                }

                if (char.ToLower(a) != char.ToLower(b))
                {
                    return false;
                }
                min++;
                max--;
            }



            throw new NotImplementedException("Waiting to be implemented.");
        }

        public static void Main(string[] args)
        {
            Console.WriteLine(IsPalindrome("Noel sees Leon."));
            Console.ReadLine(); 
        }
    }

Comparing strings with a != doesn't look right. Why not string.compare() ?

 

[Pho3nix]

Cool, but you could have also done it with an array: ToCharArray() and Linq (Select & Where)

Here e.g. is the same in Swift; using an array and higher order functions (i.e. similar concept to Linq).

extension String
{
  func isPalindrome() -> Bool {
    let lower = self.lowercaseString.unicodeScalars.filter
      { 97...122 ~= Int($0.value) }.map { String($0) }.joinWithSeparator("")
    return lower == String(lower.characters.reverse())
  }
}

"Noel sees Leon.".isPalindrome() // true

Find using the ToCharArray is the best one.
Maybe you guys can help me with the Digital root. Will post my sad code in a bit.

static int AddDigits(int num)
        {
            int val = 0;
            char[] arr = (num.ToString()).ToCharArray();
 
            if (arr.Length != 1)
            {
                foreach (var i in arr)
                {
                    val = val + int.Parse(i.ToString());
                }
                if (arr.Length != 1)
                    return AddDigits(val);
            }
            return val;
 
 
        }

 

[[)roi(]]

Comparing strings with a != doesn't look right. Why not string.compare() ?

You should review Microsoft's recommendations:

Use an overload of the String.Equals method to test whether two strings are equal.
Use the String.Compare and String.CompareTo methods to sort strings, not to check for equality.

== for String maps through to public static bool Equals(string a, string b) re String is a reference type that behaves like a value type.

 

[[)roi(]]

Find using the ToCharArray is the best one.
Maybe you guys can help me with the Digital root. Will post my sad code in a bit.

static int AddDigits(int num)
        {
            int val = 0;
            char[] arr = (num.ToString()).ToCharArray();
 
            if (arr.Length != 1)
            {
                foreach (var i in arr)
                {
                    val = val + int.Parse(i.ToString());
                }
                if (arr.Length != 1)
                    return AddDigits(val);
            }
            return val;
 
 
        }

What the context for the AddDigits method? Add the digits in a String? How about an example?

 

[Pho3nix]

What the context for the AddDigits method? Add the digits in a String? How about an example?

Basically you get a number. 64 for example. For each digit in the number parsed in, you need to add them ie, 6 + 4 until you only get 1 digit remaining.
It's digital root is :
6+4 = 10
--> 1+ 0 = 1

1 is the only digit so it is the root.

First part is figuring out how to do this in recursion. Second is doing it without recursion.

 

[[)roi(]]

Basically you get a number. 64 for example. For each digit in the number parsed in, you need to add them ie, 6 + 4 until you only get 1 digit remaining.
It's digital root is :
6+4 = 10
--> 1+ 0 = 1

1 is the only digit so it is the root.

First part is figuring out how to do this in recursion. Second is doing it without recursion.

Is this a parser for string calculator? i.e. given the following string "1 + 4 - 3" you return 2?
Or is this to simply add the successive digits in a given string "123" to return 6?