Develop Reference

List of numbers and goal -> closes sum

Regarding a question I got from one of my friends I want to ask the best possible solution
The situation is that I have a list of integers for example
2 5 6 8
And I want to get to the integers 17
I can only use each integers ones.
The closest you can get in this case is 16 because no combination leads up to 17.
public class Item
{
public int Weight { get; set; }
public int Value { get; set; }
}
public class Program
{
public static void Main()
{
var items = new[]
{
new Item {Value = 60, Weight = 10},
new Item {Value = 100, Weight = 20},
new Item {Value = 120, Weight = 30},
};
Console.WriteLine(KnapSackRecursive(items, 50));
}
public static int KnapSackRecursive(Item[] items, int capacity)
{
// keep track of the best value seen.
//TODO: Make it a list of numbers
int best = 0;
for (int i = 0; i < items.Length; i++)
{
// This is an array of the other items.
var otherItems = items.Take(i).Concat(items.Skip(i + 1)).ToArray();
// Calculate the best value without using the current item.
int without = KnapSackRecursive(otherItems, capacity);
int with = 0;
// If the current item fits then calculate the best value for
// a capacity less it's weight and with it removed from contention
// and add the current items value to that.
if (items[i].Weight <= capacity)
{
with = KnapSackRecursive(otherItems, capacity - items[i].Weight)
+ items[i].Value;
}
// The current best is the max of the with or without.
int currentBest = Math.Max(without, with);
// determine if the current best is the overall best.
if (currentBest > best)
best = currentBest;
}
return best;
}
}
Edit: It now finds the best possible weight based on the list. It'll result in finding that 20+30 = 50 so it returns 100+120 = 220 I want it to return ("Found best possible combination: 100 + 120 = 220") not just ("220")

When trying to display a hand of cards from a shuffled deck, it fills every hand with the Ace of Clubs

This is my first time using C#. I have to convert an old project from Java. The old project works, but when I attempted to convert it, something went wrong? The Card class sets the default card to the Ace of Spades, but it is displaying Ace of Clubs. Ace and Clubs are each the first listed of the enums so I guess it is not using the default?
Since it is displaying the same card I thought it would be something wrong with my shuffle method..but I am unsure at this point.
There is a Card, Deck, and Hand class. Then Enums for Suit and Face.
UPDATE: I believe the error is in the method directly below? I need to figure out how to use the 'n' in c#. It is needed in a different class.
In Java I had it as:
public Card(int n)
{
face = Face.values()[n % 13];
suit = Suit.values()[n % 4];
} //end Card (int n) method
c#:
public Card(int n) //??
{
var face = (Face) 13;
var suit = (Suit) 4;
}
The code above is in the Card class? I know that is not too helpful, but the only other way it to post ALL of the code here.
//Some of the Deck class
public void Shuffle()
{
Random ran = new Random();
for (int nextCard = 0; nextCard < deck.Length; nextCard++)
{
Card hold = deck[nextCard];
int random = ran.Next(deck.Length);
deck[nextCard] = deck[random];
deck[random] = hold;
}
}
public Card DealACard()
{
if (nextCard > 51)
{
return null;
}
return deck[nextCard++];
}
public Hand DealAHand(int handSize)
{
Hand hand = new Hand(handSize);
for (int i = 0; i < handSize; i++)
{
hand.AddCard(DealACard());
}
return hand;
}
//Some of the Hand Class
public void AddCard(Card card)
{
hand[cardsInHand] = card;
cardsInHand++;
}
public override string ToString()
{
String handToString = ""; //string to hold display format
//for loop to display each card in a hand
for (int n = 0; n < cardsInHand; n++)
{
handToString += hand[n].ToString() + "\n";
}
return handToString;
}
// Driver Class
Deck deck1 = new Deck();
int cardsToGet = 53;
do
{
Console.Write("How many cards are in one hand? ");
int handSize = Convert.ToInt32(Console.ReadLine());
// int handSize = Console.Read();
Console.Write("How many players are playing? ");
int players = Convert.ToInt32(Console.ReadLine());
cardsToGet = handSize * players;
if (cardsToGet < 53) // if to shuffle deck and display players' hands
{
deck1.Shuffle();
for (int i = 0; i < players; i++) // displays each players hand
{
Console.WriteLine("\nPlayer " + (i + 1) + ":");
Console.WriteLine(deck1.DealAHand(handSize));
}
}
else
{
Console.WriteLine("\nThere are not enough cards in the deck to deal " + players + " hands of " + handSize + " cards. Try again.\n");
}
}
while (cardsToGet > 52);
It is suppose to ask for a number of cards per hand and a number of players then displays a hand for each player without duplicating cards. Currently, it fills every players hand with Ace of Clubs. There are no errors showing.

Now that you've updated your question, this is answerable. The mistake is in your Card constructor, which no matter the value of n that you pass in, creates every card with the Face with value 13 and the Suit with value 4. You have the right method for turning an int into a Face or Suit enum (just cast it), so you just need to do the modulo operation like your Java version did:
public Card(int n)
{
var face = (Face) n % 13;
var suit = (Suit) n % 4;
}
Well, almost. The var keyword in C# just creates a local variable that's not visible outside the scope it's declared in: in this case, the constructor. What you meant to do is assign values to instance properties of your Card class. You haven't shown us what those properties are named, but I'm going to assume they're named Face and Suit (with initial uppercase as is C# naming convention); rename as appropriate:
public Card(int n)
{
this.Face = (Face) n % 13;
this.Suit = (Suit) n % 4;
}
And now your cards should all be different, rather than all being the ace of clubs.

Hello TJ and welcome to S/O, coming from other languages can be a learning curve. Same as if I switched to Java. I quickly threw this together to introduce working with lists and classes within C#. Not perfect, but does what you are looking to get at. Hope it helps. I originally wrote this with C# via a WPF application vs Console app, but the core is all the same (only thing that would be different is the "MessageBox.Show()" that shows each hand vs the Console output which I also included.
I am notorious for commenting through my code and hope this all (or most of it) makes sense as you dive into C#...
I'm starting with enums for the card faces and suits.
public enum CardFace
{
Two = 0,
Three = 1,
Four = 2,
Five = 3,
Six = 4,
Seven = 5,
Eight = 6,
Nine = 7,
Ten = 8,
Jack = 9,
Queen = 10,
King = 11,
Ace = 12
}
public enum CardSuit
{
Hearts = 0,
Clubs = 1,
Diamonds = 2,
Spades = 3
}
Next, a class to represent a single card
public class SingleCard
{
public CardFace Face { get; set; }
public CardSuit Suit { get; set; }
// place-holder for randomizing cards
public int RndNumber { get; set; }
// return the name of the card based on it's parts as single string
public string NameOfCard { get { return $"{Face} of {Suit}"; } }
}
Now, the class for building the initial deck of cards, shuffling, dealing and displaying the cards (of the entire deck, or of the individual hands)
public class DeckOfCards
{
public List<SingleCard> SingleDeck { get; private set; } = new List<SingleCard>();
public List<SingleCard> ShuffledDeck { get; private set; }
// create a single random generator ONCE and leave active. This to help prevent
// recreating every time you need to shuffle and getting the same sequences.
// make static in case you want multiple decks, they keep using the same randomizing object
private static Random rndGen = new Random();
public DeckOfCards()
{
// build the deck of cards once...
// Start going through each suit
foreach (CardSuit s in typeof(CardSuit).GetEnumValues())
{
// now go through each card within each suit
foreach (CardFace f in typeof(CardFace).GetEnumValues())
// Now, add a card to the deck of the suite / face card
SingleDeck.Add(new SingleCard { Face = f, Suit = s });
}
// so now you have a master list of all cards in your deck declared once...
}
public void ShuffleDeck()
{
// to shuffle a deck, assign the next random number sequentially to the deck.
// don't just do random of 52 cards, but other to prevent duplicate numbers
// from possibly coming in
foreach (var oneCard in SingleDeck)
oneCard.RndNumber = rndGen.Next(3901); // any number could be used...
// great, now every card has a randomized number assigned.
// return the list sorted by that random number...
ShuffledDeck = SingleDeck.OrderBy( o => o.RndNumber).ToList();
}
public void DisplayTheCards( List<SingleCard> theCards )
{
// show the deck of cards, or a single person's hand of cards
var sb = new StringBuilder();
foreach (var c in theCards)
sb = sb.AppendLine( c.NameOfCard );
MessageBox.Show(sb.ToString());
}
public void ConsoleDisplayTheCards(List<SingleCard> theCards)
{
// show the deck of cards, or a single person's hand of cards
foreach (var c in theCards)
Console.WriteLine(c.NameOfCard);
}
public List<List<SingleCard>> DealHands( int Players, int CardsPerHand )
{
// create a list of how many hands to be dealt...
// each player hand will consist of a list of cards
var Hands = new List<List<SingleCard>>(Players);
// prepare every players hand before dealing cards
for (var curPlayer = 0; curPlayer < Players; curPlayer++)
// each player gets their own list of cards
Hands.Add( new List<SingleCard>());
// prepare card sequence to deal
var nextCard = 0;
// loop for as many cards per hand
for (var oneCard = 0; oneCard < CardsPerHand; oneCard++)
{
// loop every player gets a card at a time vs one player gets all, then next player
for (var curPlayer = 0; curPlayer < Players; curPlayer++)
// add whatever the next card is to each individual's hand
Hands[curPlayer].Add(ShuffledDeck[nextCard++]);
}
return Hands;
}
}
I did not include the input of getting how many players, how many cards as you already had that. I also did not validate total cards to be dealt as you had that too. HTH

Determine if a number can be made with prepicked numbers and times

I have 2 arrays one of the types of numbers that will be used and the 2nd array is how many times that number can be used. I have a letter that determines what kind of method will be used I need to figure out how many times I can use a certain number from an array to determine a letter+number The ‘number’ is what I have to make with all the available numbers I can use. If the number cannot be made I would like to just say number cant be made or anything but allow the program to move on.
Here is what I have
int[] picksToUse = { 100, 50, 20, 10, 5, 1 };
int[] timesToUse = { 10, 10, 10, 10, 10, 10 };
string choice = Console.ReadLine();
string input = "";
if(choice.Length > 2)
{
input = choice.Substring(choice.IndexOf("$") + 1);
}
if(...){
}
else if (choice.Equals("D"))
{
int amt = Convert.ToInt32(input);
// code here to determine if number can be made with above choices
Dispense(amt, timesToUse);
}

Assuming picksToUse and timesToUse are exactly the same as you declared them, here's a way to know if you have enough of everything in stock to "pay up". It's a boolean function, which uses recursion. You would call it with the amount needed as parameter, and it would tell you right there if you have enough of everything.
Private Function HasCashInStock(amount As Integer, Optional index As Integer = 0) As Boolean
Dim billsNeeded As Integer = amount \ picksToUse(index)
If billsNeeded > timesToUse(index) Then
Return False
End If
amount -= picksToUse(index) * billsNeeded
If amount = 0 Then
Return True
End If
Return HasCashInStock(amount, index + 1)
End Function
The \ is an integer division operator (in VB.NET, at least - I'm shamelessly letting you translate this code). If you're not familiar with the integer division operator, well, when you use it with integer it gets rid of the floating numbers.
3 / 2 is not valid on integers, because it would yield 1.5.
3 \ 2 is valid on integers, and will yield 1.
That's all there is to it, really. Oh yeah, and recursion. I like recursion, but others will tell you to avoid it as much as you can. What can I say, I think that a nice recursive function has elegance.
You can also totally copy this function another time, modify it and use it to subtracts from your timesToUse() array once you know for sure that there's enough of everything to pay up.
If HasCashInStock(HereIsTheAmountAsInteger) Then
GivesTheMoney(HereIsTheAmountAsInteger)
End If
Having two functions is not the leanest code but it would be more readable. Have fun!

This is what I used to finish my project.
public static bool Validate(int amount, int[] total, int[] needed)
{
int[] billCount = total;
int[] cash = { 100, 50, 20, 10, 5, 1 };
int total = amount;
bool isValid = true;
for (int i = 0; i < total.Length; i++)
{
if(total >= cash[i])
{
billCount[i] = billCount[i] - needed[i];
}
if(billCount[i] < 0)
{
isValid = false;
break;
}
}
return isValid;
}

I got some working code. I did it with a class. I remember when I couldn't see what good classes were. Now I can't brush my teeth without a class. :-)
I force myself to do these problems to gain a little experience in C#. Now I have 3 things I like about C#.
class ATM
{
public int Denomination { get; set; }
public int Inventory { get; set; }
public ATM(int denom, int inven)
{
Denomination = denom;
Inventory = inven;
}
}
List<int> Bills = new List<int>();
List<ATM> ATMs = new List<ATM>();
private void OP2()
{
int[] picksToUse = { 100, 50, 20, 10, 5, 1 };
foreach (int d in picksToUse )
{
ATM atm = new ATM(d, 10);
ATMs.Add(atm);
}
//string sAmtRequested = Console.ReadLine();
string sAmtRequested = textBox1.Text;
if (int.TryParse(sAmtRequested, out int AmtRequested))
{
int RunningBalance = AmtRequested;
do
{
ATM BillReturn = GetBill(RunningBalance);
if (BillReturn is null)
{
MessageBox.Show("Cannot complete transaction");
return;
}
RunningBalance -= BillReturn.Denomination;
} while (RunningBalance > 0);
}
else
{
MessageBox.Show("Non-numeric request.");
return;
}
foreach (int bill in Bills)
Debug.Print(bill.ToString());
Debug.Print("Remaining Inventory");
foreach (ATM atm in ATMs)
Debug.Print($"For Denomination {atm.Denomination} there are {atm.Inventory} bills remaining");
}
private ATM GetBill(int RequestBalance)
{
var FilteredATMs = from atm in ATMs
where atm.Inventory > 0
orderby atm.Denomination descending
select atm;
foreach (ATM bill in FilteredATMs)
{
if (RequestBalance >= bill.Denomination )
{
bill.Inventory -= 1;
Bills.Add(bill.Denomination);
return bill;
}
}
return null;
}

Where is the flaw in my algorithm for consolidating gold mines?

The setup is that, given a list of N objects like
class Mine
{
public int Distance { get; set; } // from river
public int Gold { get; set; } // in tons
}
where the cost of moving the gold from one mine to the other is
// helper function for cost of a move
Func<Tuple<Mine,Mine>, int> MoveCost = (tuple) =>
Math.Abs(tuple.Item1.Distance - tuple.Item2.Distance) * tuple.Item1.Gold;
I want to consolidate the gold into K mines.
I've written an algorithm, thought it over many times, and don't understand why it isn't working. Hopefully my comments help out. Any idea where I'm going wrong?
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Mine
{
public int Distance { get; set; } // from river
public int Gold { get; set; } // in tons
}
class Solution
{
static void Main(String[] args)
{
// helper function for reading lines
Func<string, int[]> LineToIntArray = (line) => Array.ConvertAll(line.Split(' '), Int32.Parse);
int[] line1 = LineToIntArray(Console.ReadLine());
int N = line1[0], // # of mines
K = line1[1]; // # of pickup locations
// Populate mine info
List<Mine> mines = new List<Mine>();
for(int i = 0; i < N; ++i)
{
int[] line = LineToIntArray(Console.ReadLine());
mines.Add(new Mine() { Distance = line[0], Gold = line[1] });
}
// helper function for cost of a move
Func<Tuple<Mine,Mine>, int> MoveCost = (tuple) =>
Math.Abs(tuple.Item1.Distance - tuple.Item2.Distance) * tuple.Item1.Gold;
// all move combinations
var moves = from m1 in mines
from m2 in mines
where !m1.Equals(m2)
select Tuple.Create(m1,m2);
// moves in ascending order of cost
var ordered = from m in moves
orderby MoveCost(m)
select m;
int sum = 0; // running total of move costs
var spots = Enumerable.Repeat(1, N).ToArray(); // spots[i] = 1 if hasn't been consildated into other mine, 0 otherwise
var iter = ordered.GetEnumerator();
while(iter.MoveNext() && spots.Sum() != K)
{
var move = iter.Current; // move with next smallest cost
int i = mines.IndexOf(move.Item1), // index of source mine in move
j = mines.IndexOf(move.Item2); // index of destination mine in move
if((spots[i] & spots[j]) == 1) // if the source and destination mines are both unconsolidated
{
sum += MoveCost(move); // add this consolidation to the total cost
spots[i] = 0; // "remove" mine i from the list of unconsolidated mines
}
}
Console.WriteLine(sum);
}
}
An example of a test case I'm failing is
3 1
11 3
12 2
13 1
My output is
3
and the correct output is
4

The other answer does point out a flaw in the implementation, but it fails to mention that in your code, you aren't actually changing the Gold values in the remaining Mine objects. So even if you did re-sort the data, it wouldn't help.
Furthermore, at each iteration all you really care about is the minimum value. Sorting the entire list of data is overkill. You can just scan it once to find the minimum-valued item.
You also don't really need the separate array of flags. Just maintain your move objects in a list, and after choosing a move, remove the move objects that include the Mine you would otherwise have flagged as no longer valid.
Here is a version of your algorithm that incorporates the above feedback:
static void Main(String[] args)
{
string input =
#"3 1
11 3
12 2
13 1";
StringReader reader = new StringReader(input);
// helper function for reading lines
Func<string, int[]> LineToIntArray = (line) => Array.ConvertAll(line.Split(' '), Int32.Parse);
int[] line1 = LineToIntArray(reader.ReadLine());
int N = line1[0], // # of mines
K = line1[1]; // # of pickup locations
// Populate mine info
List<Mine> mines = new List<Mine>();
for (int i = 0; i < N; ++i)
{
int[] line = LineToIntArray(reader.ReadLine());
mines.Add(new Mine() { Distance = line[0], Gold = line[1] });
}
// helper function for cost of a move
Func<Tuple<Mine, Mine>, int> MoveCost = (tuple) =>
Math.Abs(tuple.Item1.Distance - tuple.Item2.Distance) * tuple.Item1.Gold;
// all move combinations
var moves = (from m1 in mines
from m2 in mines
where !m1.Equals(m2)
select Tuple.Create(m1, m2)).ToList();
int sum = 0, // running total of move costs
unconsolidatedCount = N;
while (moves.Count > 0 && unconsolidatedCount != K)
{
var move = moves.Aggregate((a, m) => MoveCost(a) < MoveCost(m) ? a : m);
sum += MoveCost(move); // add this consolidation to the total cost
move.Item2.Gold += move.Item1.Gold;
moves.RemoveAll(m => m.Item1 == move.Item1 || m.Item2 == move.Item1);
unconsolidatedCount--;
}
Console.WriteLine("Moves: " + sum);
}
Without more detail in your question, I can't guarantee that this actually meets the specification. But it does produce the value 4 for the sum. :)

When you consolidate mine i into mine j, the amount of gold in the mine j is increased. This makes consolidations from mine j to other mines more expensive potentially making the ordering of the mines by the move cost invalid. To fix this, you could re-sort the list of mines at the beginning of each iteration of your while-loop.

Roulette Wheel weakness in random number selection

I'm working on a roulette wheel class, it should function more or less like a regular roulette wheel where certain numbers can take up a larger portion of the roulette wheel and thus have a higher probability of being chosen.
So far it has passed the more basic unit tests, that is, programatically it works, I can create a roulette wheel and fill it with a bunch of generic values and it will do just that.
However when it comes to my probability testing, I decided to try it out as a 6-sided die, after 10,000,000 trials it should generate an average die roll of about 3,5 unfortunately it doesn't even come close to that the average after 10,000,000 trials is about 2,9 so I am guessing there is a weakness in my number selection somewhere? I have posted unit tests and actual code below:
public class RouletteNumber<T>
{
public readonly T Number;
public readonly int Size;
public RouletteNumber(T number, int size)
{
this.Number = number;
this.Size = size;
}
public static RouletteNumber<T>[] CreateRange(Tuple<T, int>[] entries)
{
var rouletteNumbers = new RouletteNumber<T>[entries.Length];
for (int i = 0; i < entries.Length; i++)
{
rouletteNumbers[i] = new RouletteNumber<T>(entries[i].Item1, entries[i].Item2);
}
return rouletteNumbers;
}
}
public class RouletteWheel<T>
{
private int size;
private RouletteNumber<T>[] numbers;
private Random rng;
public RouletteWheel(params RouletteNumber<T>[] rouletteNumbers)
{
size = rouletteNumbers.Length;
numbers = rouletteNumbers;
rng = new Random();
//Check if the roulette number sizes match the size of the wheel
if (numbers.Sum(n => n.Size) != size)
{
throw new Exception("The roulette number sections are larger or smaller than the size of the wheel!");
}
}
public T Spin()
{
// Keep spinning until we've returned a number
while (true)
{
foreach (var entry in numbers)
{
if (entry.Size > rng.Next(size))
{
return entry.Number;
}
}
}
}
}
[TestMethod]
public void DiceRouletteWheelTest()
{
double expected = 3.50;
var entries = new Tuple<int, int>[]
{
Tuple.Create(1, 1),
Tuple.Create(2, 1),
Tuple.Create(3, 1),
Tuple.Create(4, 1),
Tuple.Create(5, 1),
Tuple.Create(6, 1)
};
var rouletteWheel = new RouletteWheel<int>(RouletteNumber<int>.CreateRange(entries));
var results = new List<int>();
for (int i = 0; i < 10000000; i++)
{
results.Add(rouletteWheel.Spin());
}
double actual = results.Average();
Assert.AreEqual(expected, actual);
}
}

When you call Random.Next(n) it generates a random number between 0 and n-1, not between 0 and n.
Did you account for that?
In fact for a 6-sided die, you would want to call Random.Next(1, 7)

Maybe i'm not understanding it correctly but I'm guessing the problem lies here :
while (true)
{
foreach (var entry in numbers)
{
if (entry.Size > rng.Next(size))
{
return entry.Number;
}
}
}
You're calculating the rng.Next each time you do the if check.
So the first number has a 1 in 6 chance of being taken. Number 2(the next entry in numbers) then has a 2 in 6 chance of being taken(a new number is rendered between 1 and 6). But since you always start from the first you will eventually have more lower numbers.
I also don't see the need for the while(true) in a normal random generator.
I'm guessing this could would work and look like your current code :
var rndValue = rng.Next(size);
foreach (var entry in numbers)
{
if (entry.Size > rndValue)
{
return entry.Number;
}
}