I'm interested in doing something like this (C#):
int sum = 0;
for (int i = 0; i < 5; i++)
sum += i;
But I would like to do it on one line. Something like:
int sum = (embedded loop)
Is there any way to do this on one line? I'm looking to apply this to a more complex string manipulation algorithm so I can't simply replace the loop with an arithmatic formula.
So you want to loop and do something in one line?
First off, writing it in one line isn't going to make it run faster. You are still going to loop, you are still going to be O(n). For the particular problem you have in your question you can do something like:
var sum = Enumerable.Range(0,5).Sum();
This will basically make a collection of the numbers 0,1,2...4 and sum them.
More generally, since you want to do something, you might use the Aggregate function. For example:
var str = Enumerable.Range(0,5).Aggregate("",(p,c) => p + c); // Note: not efficient at all
Will take the values 0,1,...4 and do string concatenation with them (using a string builder would be better) to give you the string 01234.
Edit:
I'm trying to loop through a list of words and make each one title case, then return the string[].join(" ") of it
In that case, something like:
var result = string.Join(" ", myListOfWords.Select(w => char.ToUpper(w[0]) + w.Substring(1)));
Should work fine.
If you don't mind that 'sum' only is in scope of the for loop you could do this:
for (int i = 0, sum = 0; i < 5; sum += i, ++i) { // do something }
for(int i=0,sum = 0; i<5; sum+=i,++i){}
Related
I am working on an optimization pass for our asp.net web application and I want to shrink down and speed up as much of the backend as I can.
Is there any way to shrink down a for loop so that it becomes a lambda expression maybe?
A pure example of something that I might want to shrink down:
string outS = "";
for (int i = 0; i < length; i++)
{
outS += random.Next(0, 9).ToString();
}
return int.Parse(outS).ToString();
Instead of creating a new variable, performing some sort of function to generate it, and then returning it, is there a way where I can do all that in a single line? Like returning a lambda expression function?
Or is the current functionality the fastest way to do it anyway?
Like this silly example:
return => for(int i = 0; i < length; i++)
{
random.Next(0, 9).ToString();
}
If the logic method returns a random number that has a specified number of digits in the length variable, you could do something like this:
private int TestMethod(int length) =>
new Random().Next((int)Math.Pow(10, length - 1), (int)Math.Pow(10, length));
This form has some adventages:
No string concatenation. String concatenation is not recommended if many concatenations are performed.
The number of times a random number is requested is reduced (in the above code, the Random.Next method is only invoked once).
Nevertheless, it's a good practice that you perform a profiler comparing alternatives. You can do it with the Diagnostic Tools View in Visual Studio, and with the StopWatch class
If you're just wondering about condensing lines of code, you can use Linq's ForEach method and pass in a lambda expression.
This:
string outS = "";
for (int i = 0; i < length; i++)
{
outS += random.Next(0, 9).ToString();
}
return int.Parse(outS).ToString();
Becomes this:
string outS = "";
new List<int>(10).ForEach(_ => outS += random.Next(0, 9).ToString());
return int.Parse(outS).ToString();
I'm having trouble thinking of a logical way to achieve this. I have a method which sends a web request with a for loop that is counting up from 1 to x, the request counts up until it finds a specific response and then sends the URL + number to another method.
After this, saying we got the number 5, I need to create a string which displays as "1,2,3,4,5" but cannot seem to find a way to create the entire string, everything I try is simply replacing the string and only keeping the last number.
string unionMod = string.Empty;
for (int i = 1; i <= count; i++)
{
unionMod =+ count + ",";
}
I assumed I'd be able to simply add each value onto the end of the string but the output is just "5," with it being the last number. I have looked around but I can't seem to even think of what I would search in order to get the answer, I have a hard-coded solution but ideally, I'd like to not have a 30+ string with each possible value and just have it created when needed.
Any pointers?
P.S: Any coding examples are appreciated but I've probably just forgotten something obvious so any directions you can give are much appreciated, I should sleep but I'm on one of those all-night coding grinds.
Thank you!
First of all your problem is the +=. You should avoid concatenating strings because it allocates a new string. Instead you should use a StringBuilder.
Your Example: https://dotnetfiddle.net/Widget/qQIqWx
My Example: https://dotnetfiddle.net/Widget/sx7cxq
public static void Main()
{
var counter = 5;
var sb = new StringBuilder();
for(var i = 1; i <= counter; ++i) {
sb.Append(i);
if (i != counter) {
sb.Append(",");
}
}
Console.WriteLine(sb);
}
As it's been pointed out, you should use += instead of =+. The latter means "take count and append a comma to it", which is the incorrect result you experienced.
You could also simplify your code like this:
int count = 10;
string unionMod = String.Join(",", Enumerable.Range(1, count));
Enumerable.Range generates a sequence of integers between its two parameters and String.Join joins them up with the given separator character.
So, i have this array which contains a bunch of numbers. I want to always take 3 of those chars and make one integer out of them. I haven't found anything on this yet.
here is an example:
string number = "123456xyz";
The string is what I have, these integers are what I want
int goal1 = 123;
int goal2 = 456;
int goaln = xyz;
It should go through all the chars and always split them into groups of three. I think foreach() is going to help me, but im not quite sure how to do it.
Something like this:
var goals = new List<int>();
for (int i = 0; i + 2 < number.Length; i += 3)
{
goals.Add(int.Parse(number.Substring(i,3)));
}
This has no error checking but it shows the general outline. Foreach isn't a great option because it would go through the characters one at a time when you want to look at them three at a time.
var numbers = (from Match m in Regex.Matches(number, #"\d{3}")
select m.Value).ToList();
var goal1 = Convert.ToInt32(numbers[0]);
var goal2 = Convert.ToInt32(numbers[1]);
...
How can I use a foreach statement to loop between 2 values given by the user?
I am making an application that scans for ports, so I want the user to specify which ports to search for; here is some example code that dose not function, but should help you understand what I am looking for:
int port1 = Int32.Parse(TextBox1.Text);
int port2 = Int32.Parse(TextBox2.Text);
foreach(int between port1 and port2)
{
//do something
}
Any suggestions on how I could do this ?
No, foreach is for iterating over a collection. What you want is a for loop.
int port1 = Int32.Parse(TextBox1.Text);
int port2 = Int32.Parse(TextBox2.Text);
for(var i = port1; i <= port2; i++)
{
//do something
}
AlexD's answer is on the right track, but unfortunately misuses the second parameter of Enumerable.Range. The second parameter is count, not a bound for the range.
It should read:
Enumerable.Range(port1, (port2 - port1) + 1)
or if you don't know if port1 is less than port2:
Enumerable.Range(Math.Min(port1, port2), Math.Abs(port2 - port1) + 1)
Using array.ElementAt(0); we can get the element at index 0 of the array. Is there a method to get all the elements in an array?
string[] arr1 = {'abc', 'def', 'ghi'}
Library.Results["TEST_ACTUALVALUE"] = "The results are: " + arr1;
TEST_ACTUALVALUE is a column in my report.xls file. The above writes System.string[] in my excel file.
You already have all of the elements in the array...the array itself.
The simple answer is iterate over them:
foreach(var item in array)
{
// work with item here
}
Or if you'd rather deal with indexes:
for(var i = 0; i < array.Length; i++)
{
var item = array[i];
// work with item here
}
It's hard to know what you mean by "get all the elements in an array" because you already have all the elements....in the array.
If you mean concatinating a string from a string array then something like:
var concatinatedString = String.Concat(myArrayOfStrings);
There's a hundred ways to skin that cat. Largely it should depend on what you wish to do with all the elements. Heres the old school for loop method:
for(int i = 0; i < array.Length; i++)
{
something = array[i];
}
I'm not sure why you'd do this, but there is a array.All available. Try that?
Depending on what you want to get the elements for there are many methods you can look into
Get all the elements in an array
for(int x = 0; x < array.Length; x++)
{
something = array[x];
somethingElse = array.ElementAt(x);
}
Make an array a list to get all values:
List<T> myList = array.ToList<T>();
From here you can do all list methods with that array to get all values.
If you are trying to take the sum of every element use:
sum = array.Sum();
To get the max/min value in the array:
max = array.Max();
min = array.Min();
To get the average:
double average = array.Average(num => Convert.ToInt64(num));
There are many other ways to get all information from an array, here
The question is how to join a string array together. Solution:
... = "The results are: " + String.Join (", ", arr1);
And a note: you don't have to and should not use array.ElementAt(0) to get an element. Use array[0].
Going to go out on a limb here and recommend using a loop?
Why are you using ElementAt? You can just use the indexer:
var value = array[0];
In general:
var ithValue = array[i];
The Array class implements the IList, ICollection, and IEnumerable interfaces. So you can use any needed method of these interfaces.
Eventually, you can write foreach loop to traverse through array.
//IF the array type is string, you can follow below:
//else you need to convert to string 1st.
String Result = "";
For (int i=0; i<array.length; i++)
{
Result = Result + array[i];
}
// The result will consist all the array element.