C # Add a character in front of each character

Question

Guys, help in C # to make the addition of a character in front of each character. Example: "tour" -We are given such a word, and we have to redo it, as it were. Answer: ".tour" -and that would be a point before and after each character. How to do? C #

Accepted Answer · 2017-03-30T06:54:36

Here is a simple example of a console application. The static AddPresymbols method takes two agruments — the source word as a string and one character to be added before each symbol of the source word, and returns the result — a modified string.

 using System; using System.Linq; using System.Text; namespace ConsoleApplication { class Program { public static String AddPresymbols(String word, Char presymbol) { var result = new StringBuilder(); word.ToList().ForEach(letter => result.Append($"{presymbol}{letter}")); result.Append($"{presymbol}"); return result.ToString(); } static void Main(string[] args) { var word = "tour"; var modifiedWord = AddPresymbols(word, '.'); Console.WriteLine(modifiedWord); } } }

Added an edit so that the desired character is also added to the end of the line.

Answer 2 · 2017-03-30T07:16:33

The solution algorithm is simple: create a new line and add to it alternately a separator character or a character from the source line.

To implement, you can use the fact that the string implements the interface IEnumerable`, which means that you can use the Aggregate function

This function allows you to go through the collection and accumulate the result of the passage in the battery.

 var result = word.Aggregate(new StringBuilder(word.Length * 2 + 1), // Создаем пустой StringBuilder (sb, c) => sb.Append($".{c}"), // на каждой итерации добавляем в StringBuilder пару символов: точки и текущего символа строки sb => sb.Append(".").ToString()) // Добавляем заключительную точку и возвращаем результирующую строку

An alternative would be the following:

 var result = word.Aggregate(new StringBuilder(".", word.Length * 2 + 1), // создаем StringBuilder, в котором уже есть символ точки (sb, c) => sb.Append($"{c}."), // на каждой итерации добавляем в StringBuilder пару символов: точки и текущего символа строки sb => sb.ToString()); // возвращаем результирующую строку

As suggested in the comments: for large lines, instead of interpolated lines, it is better to use consecutive calls to Append, i.e.

 (sb, c) => Append(".").sb.Append(c)

or

 (sb, c) => sb.Append(c).Append(".")

depending on the previously selected option

In addition to Aggregate, you can use the Join function , but since this function inserts separators only inside the line, you will need to add points in front and behind, for example:

 var result = $".{string.Join<char>(".", word)}."

In this case, you must explicitly indicate that the collection has type char, otherwise an overload will be used for the string, and the dots will not be inserted anywhere.

Or you can call AsEnumerable

 var result = $".{string.Join(".", word.AsEnumerable())}."

In this case, you can omit the char type, since we explicitly pass an IEnumerable<char> and automatic type inference works.

There is a suspicion that on Append with interpolation, the memory consumption will double, stupidly at the expense of boxing char (interpolation uses it, checked).
You can fix just two consecutive Append in lambda, instead of one, for example, so word.Aggregate(new StringBuilder(word.Length * 2 + 1),(sb, c) => sb.Append(".").Append(c),sb => sb.Append(".").ToString())

slippyk slippyk 4,551 one eleven 31 · Answer 3 · 2017-03-30T07:11:01

 class Program { static void Main(string[] args) { string f = SplitStringByDot(Console.ReadLine()); Console.WriteLine(f); Console.ReadKey(); } public static string SplitStringByDot(string s) { return string.IsNullOrWhiteSpace(s) ? "WRONG!" : string.Format(".{0}.", string.Join(".", s.ToCharArray())); } }

ToCharArray can not be done so as not to create an extra array

C # Add a character in front of each character

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