CODEWITHSUNDEEP
c#
calvin ern
calvin ern

Reputation: 803

Get last 3 characters of string

How can I get only the last 3 character out from a given string?

Example input: AM0122200204

Expected result: 204

Upvotes: 71

Views: 232744

Answers (6)

SunsetQuest
SunsetQuest

Reputation: 8877

Many years lates..but here is my go at it. There are some here that accept smaller sizes and others that do not. The examples below show the output for all. I also added some benchmarks.net timings for the longer example.

string longgText = "this is some text in a string"; 
string shortText = "hi"; 
string result;

/*                Function                                 Result           Time/Source*/
/***************************************************************************************/
result = longgText.Substring(Math.Max(0,longgText.Length-6));//"string"        9.6 ns
result = shortText.Substring(Math.Max(0,shortText.Length-6));//"hi             Sunsetquest

result = longgText[^(Math.Min(6, longgText.Length))..];    // "string"         9.9 ns 
result = shortText[^(Math.Min(6, shortText.Length))..];    // "hi"             Sunsetquest

result = longgText.PadLeft(6)[^6..];                       // "string"         12.7 ns
result = shortText.PadLeft(6)[^6..];                       // "    hi"         

result = longgText[^6..];                                  // "string"         9.0 ns
result = shortText[^6..];                                  // [Exception]      Visual Sharp

result=longgText.AsSpan().Slice(longgText.Length-6).ToString();//"string"      13.0 ns
result=shortText.AsSpan().Slice(shortText.Length-6).ToString();//[Exception]   Lemon Sky

result = longgText.Substring(longgText.Length - 6);        // "string"         8.8 ns
result = shortText.Substring(shortText.Length - 6);        // [Exception]      Ian

result = Regex.Match(longgText, @"(.{6})\s*$").ToString(); // "string"         3600 ns 
result = Regex.Match(shortText, @"(.{6})\s*$").ToString(); // ""               Hari Prasad

Upvotes: 2

Юрий Война
Юрий Война

Reputation: 1

let newString = oldString.slice(-3)

Upvotes: -4

Visual Sharp
Visual Sharp

Reputation: 3996

From C# 8 Indices and ranges

Last 3 digits of "AM0122200204" string:

"AM0122200204"[^3..]

Upvotes: 26

Lemon Sky
Lemon Sky

Reputation: 697

With the introduction of Spans in C# 7.3 and .NET Core 2.1 we now have an additional way of implementing this task without additional memory allocations. The code would look as follows:

var input = "AM0122200204";

var result = input
    .AsSpan()
    .Slice(input.Length - 3);

In traditional code, every string manipulation creates a new string on the heap. When doing heavy string-based manipulations like in compilers or parsers, this can quickly become a bottleneck.

In the code above, .AsSpan() creates a safe, array-like structure pointing to the desired memory region inside the original string. The resulting ReadOnlySpan is accepted by many method overloads in libraries.

For example, we can parse the last 3 digits using int.Parse:

int value = int.Parse(result)

Upvotes: 1

Hari Prasad
Hari Prasad

Reputation: 16986

Many ways this can be achieved.

Simple approach should be taking Substring of an input string.

var result = input.Substring(input.Length - 3);

Another approach using Regular Expression to extract last 3 characters.

var result = Regex.Match(input,@"(.{3})\s*$");

Working Demo

Upvotes: 169

Ian
Ian

Reputation: 30823

The easiest way would be using Substring

string str = "AM0122200204";
string substr = str.Substring(str.Length - 3);

Using the overload with one int as I put would get the substring of a string, starting from the index int. In your case being str.Length - 3, since you want to get the last three chars.

Upvotes: 27

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