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int random = 0;
int lineNumber = 0;
for (int i = 0; i < 5; i++)
{
lineNumber++;
Random rand = new Random();
random = rand.Next(1, 1001);
Console.WriteLine($"Number {lineNumber}: {random}");
}
I want to print all the random numbers (already done) and then sum all these numbers and print the summary.
You create a new Random object every iteration which prevents you from generating a random result, it will always be the same. To sum up the values I made a variable to which you will add a random value every iteration.
using System;
public class Program
{
public static void Main()
{
Random rand = new Random();
int random = 0;
int lineNumber = 0;
int sum = 0;
for (int i = 0; i < 5; i++)
{
lineNumber++;
random = rand.Next(1, 1001); // Random number between 1 and 1000
sum += random; // Sum random values
Console.WriteLine("Number {0}: {1}", lineNumber, random); // Debug
}
Console.WriteLine("Sum of number values: " + sum);
}
}
// Number 1: 539
// Number 2: 325
// Number 3: 606
// Number 4: 919
// Number 5: 877
// Sum of number values: 3266
To add a Linq alternative to to answers:
Random rand = new Random();
var randomNumbers = Enumerable.Range(1, 5)
.Select(i => rand.Next(1, 1001));
var sumOfRandomNumbers = randomNumbers.Sum();
var linesToPrint = randomNumbers.Select((number, index) => $"Number {index}: {number}");
foreach (var line in linesToPrint)
{
Console.WriteLine(line);
}
Console.WriteLine(sumOfRandomNumbers);
Not only can you move the Random initialization outside the for-loop, you can also remove your linenumber count since this is already encapsulated in the iterable you use in your for-loop: i.
I hereby suggest a solution that also takes advantage of the fact that you can increase a variable with another variable that gets its value assigned at the same time.
int numberCount = 5;
int sum = 0;
int random;
Random rand = new Random();
for (int i = 0; i < numberCount; i++)
{
sum += random = rand.Next(1, 1001);
Console.WriteLine($"Number {i+1}: {random}");
}
Console.WriteLine($"Sum: {sum}");
Related
I'm trying to create an array list using random numbers. But sometimes I get a zero in results. I do not understand why.
I'm grateful if anyone can explain.
int[] number = new int[6];
Random rnd = new Random();
for (int i = 0; i < number.Length; i++)
{
int random = rnd.Next(1, 26);
if (!number.Contains(random))
{
number[i] = random;
}
}
foreach (int nr in number)
{
Console.Write("|" + nr + "|");
}
//results
|6||12||0||22||25||11|
int[] number = new int[6];
Here number array is created with default int value i.e 0
The issue with your code is in some cases this value is not getting updated due to the check
if (!number.Contains(random))
You can change your code to include a loop to guarantee your random number doesn't lie in the array.
int[] number = new int[6];
Random rnd = new Random();
for (int i = 0; i < number.Length; i++)
{
int random = rnd.Next(1, 26);
while (number.Contains(random))
{
random = rnd.Next(1, 26);
}
number[i] = random;
}
foreach (int nr in number)
{
Console.Write("|" + nr + "|");
}
Please note that current approach is quite performance hungry as for every new random value we are iterating through entire array everytime to check if it exists. You can reduce the performance by using as HashSet<int> if possible
When you declare the array in following statement it initializes with 6 integers as 0
int[] number = new int[6];
While the random number generated for each array element, check for duplication in following statement may have resulted false
if (!number.Contains(random))
That's why it was never updated to new assigned number.
You can add else condition to it and regenerate random number
Just use your debugger to step through your code and inspect your variables to see what's happening. Apart from all the suggestions here, which are bad because they can loop way too many times or even forever, you appear to want to get 6 random, unique numbers between 1 and 26.
The de facto way to do that, is to generate a list with those numbers (Enumerable.Range()), shuffle them (Fisher-Yates) and Take() the first six.
Use while loop.
int[] number = new int[6];
Random rnd = new Random();
int i = 0;
while (i < number.Length)
{
int random = rnd.Next(1, 26);
if (!number.Contains(random))
{
number[i] = random;
i++;
}
}
foreach (int nr in number)
{
Console.Write("|" + nr + "|");
}
I'm very new to coding and I just can't wrap my head around Loops/Arrays/Randoms. I understand the concept but when it comes to applying it, I'm just lost.
Here I'm trying to generate 100 random numbers between 1-1000 and it has to output the maximum value. Here's my code so far:
Random rnd = new Random();
int nums = rnd.Next(0, 1001);
for (int i = 1; i <= 100; i++)
{
}
Console.WriteLine(nums);
Console.ReadLine();
It's only giving me one number. :(
I'd greatly appreciate any help!
Thanks!
You can accumulate your random generated number to the array and then by using Max function of the array you can find the maximum value
class Program
{
public static void Main(string[] args)
{
Random rnd = new Random();
int[] intArr = new int[100];
for (int i = 0; i < intArr.Length; i++)
{
int num = rnd.Next(1, 1000);
intArr[i] = num;
Console.WriteLine(num);
}
Console.WriteLine();
int maxNum = intArr.Max();
Console.WriteLine("The max num is:" + maxNum);
Console.ReadLine();
}
}
Click to watch online demo
You need to call rnd.Next() inside loop.
Random rnd = new Random();
for (int i = 1; i <= 100; i++)
{
int nums = rnd.Next(0, 1001);
Console.WriteLine(nums);
}
Console.ReadLine();
A good approach would be initializing a variable that stores your max. Then generate a random number within your iterative block and if it is greater than your max, set it as the new max.
Random r = new Random();
int max = 0; //declare our max variable
for(int i = 0; i < 100; i++)
{
int rand = r.Next(0, 1001);
if(rand > max) //if the new random value is greater than our max, set max = rand
max = rand;
}
Console.WriteLine(max); //Output the maximum value
Console.ReadLine();
If you want to output every random value and then output the max out of all the values generated, simply modify the code above by outputting rand within your loop as well.
Hope this helps!
I am not sure, are you asking like this?
Random random = new Random();
int[] nums = new int[100];
// when for loop ends, nums are full of 100 numbers
for (int i = 0; i < nums.Length; i++)
{
int newNum = random.Next(1, 1000);
// show every number
Console.WriteLine(newNum);
nums[i] = newNum;
}
// get the max number
var maxNum = nums.Max();
Console.WriteLine(maxNum);
If you want to see the code for Loops/Arrays/Randoms all working together you can use the below with the comments walking through what each line is doing (Working .NET Fiddle Example)
public static void Main()
{
// Pass in what range we want our randomly generated numbers to be in
// In your case, between 1 - 1000 and we want to create 100 of them.
//(See GenerateRandomNumbers())
var random = GenerateRandomNumbers(1, 1000, 100);
//Take our newly returned randomly created numbers and
//pass them to our GetMaxNumber method so it can find the Max number
//See (GetMaxNumber())
var result = GetMaxNumber(random);
//We now have our max number; print it to the Console.
Console.WriteLine("Max: " + result);
}
public static int GetMaxNumber(params int[] inputs)
{
//Create a variable that will store the largest number we find in our array
int max = inputs[0];
//Iterate (loop) through all of the 100 values in our array that we passed in
//Here we define "input" which will hold the value for each value in inputs as we check
//if the value of input is greater than our current value of max. If it is greater than our
//current value of max, then we need to update max to now be equal to the value of our input.
//Note: it will do this comparison 100 times beginning with the first value in the inputs array
foreach (var input in inputs)
{
if (input > max)
{
//input's value is greater than the current value of max; update max so that it is equal to the current value of input.
max = input;
}
//no more code; return to top of foreach loop and set input to the next value in inputs
}
//When we get here, it means our foreach loop has completed going through and comparing all 100 values of inputs to see which value is the largest.
//now return this value to Main()
return max;
}
public static int[] GenerateRandomNumbers(int beginRange, int endRange, int maxNumbers)
{
// Instantiate random number generator
Random rnd = new Random();
//Generate and display
int[] intArr = new int[maxNumbers];
//Generate 100 numbers with numbers between 1 and 1000
for (int i = 0; i < intArr.Length; i++)
{
int num = rnd.Next(beginRange, endRange);
intArr[i] = num;
}
return intArr;
}
This question already has answers here:
Generating random, unique values C#
(17 answers)
Closed 4 years ago.
I want to generate random numbers and put them in an array, but they should only appear once in this array. It's like a mini lotto game.
This is the code I have right now:
int[] arrA = new int[10];
Random random = new Random();
for (int i = 0; i <= arrA.Length -1; i++)
{
arrA[i] = random.Next(1, 15);
Console.WriteLine(arrA[i]);
}
Console.ReadKey();
Random numbers are generated and put in this Array. I only need to know how it's possible to program that they only appeare once.
Use HashSet<T>. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.
Something like this:
using System;
using System.Collections.Generic;
HashSet<int> numbers = new HashSet<int>();
for (int i = 0; i < 10; i++)
{
// Start with a random number
//
int value = random.Next(1,15);
// Check whether you already have that number
// Keep trying until you get a unique
//
while (numbers.Contains(value)) {
value = random.Next(1,15);
}
// Add the unique number to the set
numbers.Add(value);
}
foreach (int i in numbers)
{
Console.Write(" {0}", i);
}
int[] arrA = new int[10];
Random random = new Random();
for (int i = 0; i <= arrA.Length - 1; i++)
{
var number = random.Next(1, 15);
while (arrA.Any(n => n == number))
{
number = random.Next(1, 15);
}
arrA[i] = number;
Console.WriteLine(arrA[i]);
}
Console.ReadKey();
Everytime you generate a new number, instead of putting it in the array right away check the array from the start to the current position (using a for-loop). If it's not there insert the generated number, otherwise generate a new one and repeat the process.
This question already has answers here:
Random number generator with no duplicates
(12 answers)
Closed 6 years ago.
int Min = 0;
int Max = 20;
int[] test2 = new int[5];
Random randNum = new Random();
for (int i = 0; i < test2.Length; i++)
{
test2[i] = randNum.Next(Min, Max);
}
How can I make sure that the numbers between 0 and 20 will not be the same in the array ? For example I don't want to have in the array twice the number 5.
And how to do it with a List ? or array is better ?
Create an array of Max length and insert numbers from 0 to Max. Then use a random algorithm to choose one element of the array (possibly mod(Max-chosenElementsNumber)). After delete element from array. Done.
Or use LINQ. (By generating a sequence between Min and Max with Enumerable.Range):
var rnd = new Random();
var res = Enumerable.Range(Min, Max - Min + 1).OrderBy(x => rnd.Next()).ToList();
And if you want to pick specific number of the sequence you can use Take method. Like this:
var res = Enumerable.Range(Min, Max - Min + 1).OrderBy(x => rnd.Next()).Take(5).ToList();
You can use an HashSet<int>, it doesn't allow duplicates.
int Min = 0;
int Max = 20;
var test2 = new HashSet<int>();
Random randNum = new Random();
while(test2.Count < 5)
{
test2.Add(randNum.Next(Min, Max));
}
You can also randomize with LINQ:
int Min = 0;
int Max = 20;
Random randNum = new Random();
var test2 = Enumerable.Range(Min, Max - Min + 1)
.OrderBy(x => randNum.Next())
.Take(5)
.ToArray();
Just continue to get another random number if you get a duplicated one.
int Min = 0;
int Max = 20;
int[] test2 = new int[5];
Random randNum = new Random();
for (int i = 0; i < test2.Length; i++)
{
int r;
do
{
r = randNum.Next(Min, Max);
} while (test2.Contains(r));
test2[i] = r;
}
This is normal method of sorting integers 0 to 19
List<KeyValuePair<int, int>> numbers = new List<KeyValuePair<int, int>>();
Random randNum = new Random();
for (int i = 0; i < 20; i++)
{
numbers.Add(new KeyValuePair<int,int>(i, randNum.Next()) );
}
numbers = numbers.OrderBy(x => x.Value).ToList();
Console.WriteLine(string.Join(",", numbers.Select(x => x.Key).ToArray()));
Console.ReadLine();
System.Random generator = new Random(DateTime.Now.Millisecond);
int[] lotteryNumber = new int[7];
Console.WriteLine("Your lottery numbers: ");
for (int i = 0; i<7; i++)
{
lotteryNumber[i] = generator.Next(1, 37);
Console.Write("{0} ",lotteryNumber[i]);
}
Console.ReadLine();
I need to make a program that prints 7 lottery numbers, but without duplicates. The code above prints 7 random numbers in the range of (1-37), but duplicates appaer. I need a way to prevent duplicate numbers from appearing.
The simplest approach IMO would be to generate a sequence of all the possible numbers (i.e. 1-37), shuffle the collection, then take the first seven results.
Searching on Stack Overflow for "Fisher-Yates shuffle C#" will find lots of examples.
In fact, you could modify the Fisher-Yates shuffle to yield results as you took them, so you could write a method such as:
var numbers = Enumerable.Range(1, 37).Shuffle().Take(7).ToList();
You could take a dictionary but make sure that you prevent duplicate key insertion. Keys of dictionary would serve as the unique numbers you need
You could toss them into a HashSet<int>. If you Add and it returns false, generate a new number.
If you're trying to pick numbers from a range without repetitions, you need to create an array of all the possible numbers and then "shuffle" a random selection out:
int[] allPossibleNumbers = Enumerable.Range(1, 37).ToArray();
int[] lotteryNumber = new int[7];
for (int i = 0; i < 7; i++)
{
int index = r.Next(i, 37);
lotteryNumber[i] = allPossibleNumbers[index];
allPossibleNumbers[index] = allPossibleNumbers[i];
// This step not necessary, but allows you to reuse allPossibleNumbers
// rather than generating a fresh one every time.
// allPossibleNumbers[i] = lotteryNumber[i];
}
Generate a list with your 37 items.
Then in your for, select one and delete the selected
Maybe this could help, if you get the existing number just try to find new one that isn't in the array:
static void Main(string[] args)
{
System.Random generator = new Random(DateTime.Now.Millisecond); int[] lotteryNumber = new int[7];
Console.WriteLine("Your lottery numbers: ");
for (int i = 0; i < 7; i++)
{
int lNumber = 0;
do
{
lNumber = generator.Next(1, 37);
}
while (lotteryNumber.Contains(lNumber));
lotteryNumber[i] = lNumber;
Console.Write("{0} ", lotteryNumber[i]);
}
Console.ReadLine();
}
HashSet<int> set = new HashSet<int>();
System.Random generator = new Random(DateTime.Now.Millisecond);
while(set.Count < 7){
set.Add(generator.Next(1,37);
}
That should work, since a HashSet will automatically ignore duplicates. Just loop until the set reaches the number of units you need. Only potential problem is it has the POTENTIAL (unlikely) to loop for a long time, but it should eventually respond.
so I took your original code...found some logic errors and added the fix you were looking for to prevent random number duplicates.
Enjoy!
System.Random generator = new Random(DateTime.Now.Millisecond);
int[] lotteryNumber = new int[7];
int lowerBounds = 1;
int upperBounds = 8;
int maxNumberLotteryValues = 7;
if ( ( upperBounds - lowerBounds ) < (maxNumberLotteryValues))
{
Console.Write("Warning: Adjust your upper and lower bounds...there are not enough values to create a unique set of Lottery numbers! ");
}
else
{
Console.WriteLine("Your lottery numbers: ");
for (int i = 0; i < maxNumberLotteryValues; i++)
{
int nextNumber = generator.Next(lowerBounds, upperBounds);
int count = lowerBounds; //Prevent infinite loop
while ((lotteryNumber.Contains(nextNumber))
&& (count <= upperBounds))
{
nextNumber = generator.Next(lowerBounds, upperBounds);
count++; //Prevent infinite loop
}
lotteryNumber[i] = nextNumber;
Console.Write("{0} ", lotteryNumber[i]);
}
}
Console.ReadLine();
const int nBalls = 37;
const int nPicks = 6;
int[] balls = new int[nPicks];
Random rnd = new Random(DateTime.Now.Millisecond);
int remainingBalls=nBalls;
int remainingPicks=nPicks;
for (int i = 1; i <= nBalls; i++)
{
if (rnd.Next(1, remainingBalls+1) <= remainingPicks)
balls[--remainingPicks]=i;
remainingBalls--;
}
Console.WriteLine(string.Join(",",balls));
Will outperform Shuffle and HashSet methods as nPicks/nBalls gets larger.