Develop Reference

Generate All Possible Combinations of A Password When Given the List of Integers

I have a list of integers:
List <int> allPossibleValues;
The length of the password:
int passwordLength = 2;
I should generate all possible combinations of the password with
the integers from the list:
List <int> allPossibleValues = new List<int>() { 1, 2, 4};
int passwordLength = 2;
Expected result:
List<string> {
"11", "22", "44", "12", "21", "14", "41", "24", "42"
};
How can I create a logic to implement this?

Well, you can put it like this:
Code:
using System.Linq;
...
// Let's do it a bit more general - <T> - and enumerate any items of alphabet
private static IEnumerable<string> Passwords<T>(List<T> alphabet, int size) {
int[] current = new int[size];
do {
yield return string.Concat(current.Select(i => alphabet[i]));
for (int i = 0; i < current.Length; ++i)
if ((current[i] = (current[i] + 1) % alphabet.Count) != 0)
break;
}
while (!current.All(i => i == 0));
}
Demo:
List <int> allPossibleValues = new List<int>() { 1, 2, 4};
int passwordLength = 2;
string[] passwords = Passwords(allPossibleValues, passwordLength).ToArray();
var report = string.Join(", ", passwords);
Console.Write(report);
Outcome:
11, 21, 41, 12, 22, 42, 14, 24, 44

You could just use two for cycles to iterate through your Input list twice, combine the values and add the combined value to a new list.

how to multiply each element in an array with a loop c#

im trying to multiply each element in three different arrays by 2 with a loop but im having trouble. im really new at this so please excuse any obvious mistakes lol im not even sure ive im using the right kind of loop but heres what i have so far:
int[] firstArray = new int[] { 1, 2, 5, 6, 9 };
int[] secondArray = new int[] { 12, 3, 8, 20, 7 };
int[] thirdArray = new int[] { 2, 4, 6, 8, 10, 12 };
foreach(new int [5] in firstArray)
{
int newArray1= firstArray.Length * 2;
Console.WriteLine(newArray1);
}
i want it to print out the first new array as "2, 4, 10, 12, 18" in the console but when i run it, i get the error type and identifier are both required in a foreach statement.
any help would be greatly appreciated!

Do this with Linq
int[] resultFirstArray = firstArray.Select(r=> r * 2).ToArray();
int[] resultSecondArray = secondArray.Select(r=> r * 2).ToArray();
int[] resultThirdArray = thirdArray.Select(r=> r * 2).ToArray();
Or you can use Array.ConvertAll
Array.ConvertAll converts an entire array. It converts all elements in one array to another type.
var resultFirstArray = Array.ConvertAll(firstArray, x => 2 * x);
var resultSecondArray = Array.ConvertAll(secondArray, x => 2 * x);
var resultThirdArray = Array.ConvertAll(thirdArray, x => 2 * x);

If you just want to show the doubled values:
foreach(int value in firstArray)
{
Console.WriteLine(2 * value);
}
If you want to double the values in the array, then:
for(int i = 0 ; i < firstArray.Length ; i++)
{
firstArray[i] *= 2;
}
Then perhaps to show those values:
foreach(int value in firstArray)
{
Console.WriteLine(value);
}
If you want to create a new array with the values doubled:
var doubledArray = Array.ConvertAll(firstArray, x => 2 * x);
And to output those values:
foreach(int value in doubledArray)
{
Console.WriteLine(value);
}

C# - How to find the most common and the least common integers in an array?

I was asked to make a Dice program with two arrays (one for each dice) and add the two results, e.g.: 2 (dice 1) + 6 (dice 2) = 8.
The program must roll the dices 100 times and show the sum each time.
I could do it so far, but the program also must show which sum is the most frequent, and which sum is the least frequent.
Like this: sum = [2, 2, 2, 2, 3, 3, 4, 4, 5, 6, 6]. Most common: 2; Least common: 5.
How can I do it?
This is how my code looks like:
static void Main(string[] args)
{
Random gerador = new Random();
int[] soma = new int[100];
int rolagem = 0;
for(int i = 0; i < soma.Length; i++)
{
rolagem = 0;
rolagem += gerador.Next(6) + 1;
rolagem += gerador.Next(6) + 1;
soma[i] = rolagem;
}
var mais = soma.GroupBy(item => item).OrderByDescending(g => g.Count()).Select(g => g.Key).First();
//NEED TO FIND OUT LEAST COMMON SUM
for (int j = 1; j < soma.Length; j++)
{
Console.Write("{0} ", soma[j]);
}
Console.WriteLine("Soma mais frequente: {0}, Soma menos frequente: {1}", mais, menos);
Console.ReadKey();
}

You're almost there, you can find the least common one similarly:
var array = new[] { 1, 1, 1, 1, 4, 2, 2, 3, 3, 3, 5, 5 };
var result = array.GroupBy(i => i).OrderBy(g => g.Count()).Select(g => g.Key).ToList();
var mostCommon = result.Last();
var leastCommon = result.First();

If you have code that rolls the dice 100 times, you are pretty close. All you need to do is frequency counters.
A roll of a pair of dice yields a number between 2 and 12, inclusive. Make an int count[13] array before entering the loop.
In the loop each time you have two numbers, say, d1 and d2, increment the count as follows:
count[d1+d2]++;
Once the loop is over, find the highest and the lowest numbers in the array between indexes 2 and 12, inclusive. The index of the highest number will be the number with the highest roll count; the index of the lowest number will be the number with the lowest roll count.

Tuple<int, int> least = new Tuple<int, int>(-1, -1), most = new Tuple<int, int>(-1, -1);
List<int> arr = new List<int> { 2, 2, 2, 2, 3, 3, 4, 4, 5, 6, 6 };
var grp = arr.GroupBy(x => x).Select(x=>x).ToList();
foreach (var item in grp)
{
if (least.Item2 == -1 || least.Item2>item.Count())
{
var x = new Tuple<int, int>(item.Key, item.Count());
least = x;
}
if (most.Item2 == -1 || most.Item2 < item.Count())
{
var x = new Tuple<int, int>(item.Key, item.Count());
most = x;
}
}
Console.WriteLine("Least : "+least.Item1+" repeated " + least.Item2+"times");
Console.WriteLine("Most : "+most.Item1 + " repeated " + most.Item2 + "times");
Or as m1kael suggested,
Tuple<int, int> least = new Tuple<int, int>(-1, -1), most = new Tuple<int, int>(-1, -1);
List<int> arr = new List<int> { 2, 2, 2, 2, 3, 3, 4, 4, 5, 6, 6 };
var grp = arr.GroupBy(x => x).OrderBy(x=>x.Count()).Select(x => x.Key).ToList();
Console.WriteLine("Least : "+ grp.First());
Console.WriteLine("Most : "+ grp.Last());

There is a small chance for more than one most or least common:
var a = Enumerable.Repeat(new Random(), 100).Select(r => r.Next(6) + r.Next(6) + 2);
var groups = a.GroupBy(i => i).GroupBy(g => g.Count(), g => g.Key).OrderBy(g => g.Key).ToList();
var mostCommon = string.Join(", ", groups.Last());
var leastCommon = string.Join(", ", groups[0]);

How can I get the sum (average) value of three lists in C#?

I have three lists which each list represents only 0s and 1s which related to the pixel values of three images.
My question is how can I get the sum (average) of those three lists and represent it in a new list?
here is example of my image1:
List<int> image1 = new List<int>();
int blackColor = 0;
for (int x = 0; x < bmp1.Width; x++)
{
for (int y = 0; y < bmp1.Height; y++)
{
Color color = bmp1.GetPixel(x, y);
if (color.ToArgb() == Color.Black.ToArgb())
{
image1.Add(0);
blackColor++;
}
else
{
image1.Add(1);
}
}
}

Let me makes sure I understand the problem. You have three lists of the same length:
list A: 1, 2, 4, 3
list B: 3, 2, 4, 1
List C: 2, 7, 1, 8
and you wish to get a third list that is the average of each:
List D: 2, 4, 3, 4
Yes?
This is a job for zip join.
var sumOfFirstTwo = list1.Zip(list2, (x, y)=>x + y);
sumOfFirstTwo is now the sequence that is the sum of the first two lists.
var sumOfAllThree = sumOfFirstTwo.Zip(list3, (x, y)=>x + y);
sumOfAllThree is now the sequence that is the sum of all three lists.
var average = sumOfAllThree.Select(x=>x/3).ToList();
Make sense?

This works for an arbitrary number of lists
var firstList = new[] { 1, 2, 3, 1 };
var secondList = new[] { 2, 3, 1, 1 };
var thirdList = new[] { 3, 1, 2, 2 };
var lists = new[] { firstList, secondList, thirdList };
var listLengths = lists.Select(x => x.Count());
if (listLengths.Distinct().Count() != 1)
throw new Exception("Line lengths must be the same");
var lengthOfEachList = listLengths.First();
var averages = new List<double>();
for (var i = 0; i != lengthOfEachList; ++i) {
averages.Add(lists.Average(x => x[i]));
}
The LINQ way would be
var averages = Enumerable.Range(0, lengthOfEachList).Select(x => lists.Average(y => y[x]));

To find the top 3 maximum repeated numbers in a integer array

I want to find the top 3 maximum repeated numbers in a Integer array?
Below is the piece of code which I have tried but I couldn't find the desired result:
static void Main(string[] args)
{
int[,] numbers = {
{1, 2, 0, 6 },
{5, 6, 7, 0 },
{9, 3, 6, 2 },
{6, 4, 8, 1 }
};
int count = 0;
List<int> checkedNumbers = new List<int>();
foreach (int t in numbers)
{
if (!checkedNumbers.Contains(t))
{
foreach (int m in numbers)
{
if (m == t)
{
count++;
}
}
Console.WriteLine("Number {0} is Repeated {1} Times ", t, count);
count = 0;
checkedNumbers.Add(t);
}
}
Console.ReadLine();
}

You can use GroupBy from LINQ then OrderByDescending based on count in each group:
var result = list.GroupBy(i => i)
.OrderByDescending(g => g.Count())
.Select(g => g.Key)
.Take(3);
Edit: With your code, you can use OfType to flatten your matrix then use the code above:
int[,] numbers = {
{1, 2, 0, 6 },
{5, 6, 7, 0 },
{9, 3, 6, 2 },
{6, 4, 8, 1 }
};
var list = numbers.OfType<int>();

int[] numbers = {1, 2, 3, 5, 6, 32, 2, 4, 42, 2, 4, 4, 5, 6, 3, 4};
var counts = new Dictionary<int, int>();
foreach (var number in numbers)
{
counts[number] = counts[number] + 1;
}
var top3 = counts.OrderByDescending(x => x.Value).Select(x => x.Key).Take(3);

Hint:
You can do this with the help of LINQ.
This is the code to find most frequest occuring element:-
List<int> list = new List<int>() { 1,1,2,2,3,4,5 };
// group by value and count frequency
var query = from i in list
group i by i into g
select new {g.Key, Count = g.Count()};
// compute the maximum frequency
int frequency = query.Max(g => g.Count);
// find the values with that frequency
IEnumerable<int> modes = query
.Where(g => g.Count == frequency)
.Select(g => g.Key);
// dump to console
foreach(var mode in modes) {
Console.WriteLine(mode);
}
In the same manner you can find the other two also.

I see that none of the existing answers provide an explanation, so I will try to explain.
What you need to do is to count how many times each item appears in the array. To do that, there are various methods (dictionaries, linq etc). Probably it would be easiest to use a dictionary which contains the number, and how may times it appeared:
int numbers[] = {1, 3, 6, 10, 9, 3, 3, 1, 10} ;
Dictionary<int, int> dic = new Dictionary<int, int>();
Now iterate through every element in numbers, and add it to the dictionary. If it was already added, simply increase the count value.
foreach (var i in numbers)
{
dic[i]++; // Same as dic[i] = dic[i]+1;
}
The dictionary will automatically adds a new item if it doesn't exist, so we can simply do dic[i]++;
Next, we need to get the highest 3 values. Again, there are many ways to do this, but the easiest one would be to sort it.
var sorted_dic = dic.OrderByDescending(x => x.Value);
Now the first 3 items in sorted_dic are going to be the 3 values you are looking for.
There are various methods to get only these 3, for example using the Take method:
var first_3 = sorted_dic.Take(3);
Now you can iterate through these 3 values, and for example print them on the screen:
foreach (var i in first_3)
{
Console.Write("{0} appeared {1} times.", i.Key, i.Value);
}