如何仅在字符串的第一句中找到字母出现的次数？

Question

I want to find number of letter "a" in only first sentence. The code below finds "a" in all sentences, but I want in only first sentence.

static void Main(string[] args)
{
    string text;  int k = 0;
    text = "bla bla bla. something second. maybe last sentence.";

    foreach (char a in text)
    {
        char b = 'a';
        if (b == a)
        {
            k += 1;
        }
    }

    Console.WriteLine("number of a in first sentence is " + k);
    Console.ReadKey();
}

Answer 1

This will split the string into an array seperated by '.', then counts the number of 'a' char's in the first element of the array (the first sentence).

var count = Text.Split(new[] { '.', '!', '?', })[0].Count(c => c == 'a');

This example assumes a sentence is separated by a . , ? or ! . If you have a decimal number in your string (eg 123.456), that will count as a sentence break. Breaking up a string into accurate sentences is a fairly complex exercise.

Answer 2

You didn't define "sentence", but if we assume it's always terminated by a period ( . ), just add this inside the loop:

if (a == '.') {
    break;
}

Expand from this to support other sentence delimiters.

Answer 3

This is perhaps more verbose than what you were looking for, but hopefully it'll breed understanding as you read through it.

public static void Main()
    {
        //Make an array of the possible sentence enders. Doing this pattern lets us easily update
        // the code later if it becomes necessary, or allows us easily to move this to an input
        // parameter
        string[] SentenceEnders = new string[] {"$", @"\.", @"\?", @"\!" /* Add Any Others */};
        string WhatToFind = "a"; //What are we looking for? Regular Expressions Will Work Too!!!
        string SentenceToCheck = "This, but not to exclude any others, is a sample."; //First example
        string MultipleSentencesToCheck = @"
        Is this a sentence
        that breaks up
        among multiple lines?
        Yes!
        It also has
        more than one
        sentence.
        "; //Second Example

        //This will split the input on all the enders put together(by way of joining them in [] inside a regular
        // expression.
        string[] SplitSentences = Regex.Split(SentenceToCheck, "[" + String.Join("", SentenceEnders) + "]", RegexOptions.IgnoreCase);

        //SplitSentences is an array, with sentences on each index. The first index is the first sentence
        string FirstSentence = SplitSentences[0];

        //Now, split that single sentence on our matching pattern for what we should be counting
        string[] SubSplitSentence = Regex.Split(FirstSentence, WhatToFind, RegexOptions.IgnoreCase);

        //Now that it's split, it's split a number of times that matches how many matches we found, plus one
        // (The "Left over" is the +1
        int HowMany = SubSplitSentence.Length - 1;

        System.Console.WriteLine(string.Format("We found, in the first sentence, {0} '{1}'.", HowMany, WhatToFind));

        //Do all this again for the second example. Note that ideally, this would be in a separate function
        // and you wouldn't be writing code twice, but I wanted you to see it without all the comments so you can
        // compare and contrast

        SplitSentences = Regex.Split(MultipleSentencesToCheck, "[" + String.Join("", SentenceEnders) + "]", RegexOptions.IgnoreCase | RegexOptions.Singleline);
        SubSplitSentence = Regex.Split(SplitSentences[0], WhatToFind, RegexOptions.IgnoreCase | RegexOptions.Singleline);
        HowMany = SubSplitSentence.Length - 1;

        System.Console.WriteLine(string.Format("We found, in the second sentence, {0} '{1}'.", HowMany, WhatToFind));
    }

Here is the output:

We found, in the first sentence, 3 'a'.
We found, in the second sentence, 4 'a'.

Answer 4

       string SentenceToCheck = "Hi, I can wonder this situation where I can do best";

      //Here I am giving several way to find this
        //Using Regular Experession

        int HowMany = Regex.Split(SentenceToCheck, "a", RegexOptions.IgnoreCase).Length - 1;
        int i = Regex.Matches(SentenceToCheck, "a").Count;
        // Simple way

        int Count = SentenceToCheck.Length - SentenceToCheck.Replace("a", "").Length;

        //Linq

        var _lamdaCount = SentenceToCheck.ToCharArray().Where(t => t.ToString() != string.Empty)
            .Select(t => t.ToString().ToUpper().Equals("A")).Count();

       var _linqAIEnumareable = from _char in SentenceToCheck.ToCharArray()
                                 where !String.IsNullOrEmpty(_char.ToString())
                                 && _char.ToString().ToUpper().Equals("A")
                                 select _char;

        int a =linqAIEnumareable.Count;

        var _linqCount = from g in SentenceToCheck.ToCharArray()
                         where g.ToString().Equals("a")
                         select g;
        int a = _linqCount.Count();

Answer 5

Simply "break" the foreach(...) loop when you encounter a "." (period)

Answer 6

Well, assuming you define a sentence as being ended with a '.''

Use String.IndexOf() to find the position of the first '.'. After that, searchin a SubString instead of the entire string.

Answer 7

1. find the place of the '.' in the text ( you can use split )
2. count the 'a' in the text from the place 0 to instance of the '.'