How to count character occurrence in a string?

[academyofzhuang]

I want to count char occurrence in a string by building a dictionary.

dict: <character, occurence>.

But I did not figure out how to build such dictionary;

First try.

public static class Test
{
	public static void Main(string[] args)
	{
		Dictionary<string, int>() d;
		string s = "abcda";
		// what is the type of s[0]
		d[s[0]] = 1;	
	}

}

Fusion reports s[0] is not a string: test.fu(9): ERROR: Cannot convert '(-128 .. 65535)' to 'string'

Second try.

public static class Test
{
	public static void Main(string[] args)
	{
		Dictionary<int, int>() d;
		string s = "abcda";
		// what is the type of s[0]
		d[s[0]] = 1;	
	}

}

to Java:

// Generated automatically with "fut". Do not edit.
import java.util.HashMap;

public final class Test
{
	private Test()
	{
	}

	public static void main(String[] args)
	{
		final HashMap<Integer, Integer> d = new HashMap<Integer, Integer>();
		String s = "abcda";
		d.put(s.charAt(0), 1);
	}
}

The java code won't compile becuase mismatch of key type: char and Integer.

[pfusik]

You should first decide what you mean by "character" and understand that different programming languages have different native string encodings. For instance, Java uses UTF-16.

You can count code points this way:

public static class Test
{
	public static void Main(string[] args)
	{
		Dictionary<int, int>() d;
		string s = "abcda";
		foreach (int c in s)
			d[c] = d.ContainsKey(c) ? d[c] + 1 : 1;
		foreach ((int c, int count) in d)
			Console.WriteLine($"Code point {c}: {count} occurrences");
	}
}

but note that non-ASCII code points will differ from language to language.