我想找到字符串中特定单词的出现次数。
我在网上搜索过，发现很多答案
但他们都没有给我准确的结果。
我想要的是：
输入：
I have asked the question in StackOverflow. Therefore i can expect answer here.
“The”关键字的输出：
The keyword count: 2
注意：不应该在句子中考虑“因此”中的“The”。
基本上我想匹配整个单词并得到计数。
试试这样吧
var searchText=" the ";
var input="I have asked the question in StackOverflow. Therefore i can expect answer here.";
var arr=input.Split(new char[]{' ','.'});
var count=Array.FindAll(arr, s => s.Equals(searchText.Trim())).Length;
Console.WriteLine(count);
编辑
为您的搜索句子
var sentence ="I have asked the question in StackOverflow. Therefore i can expect answer here.";
var searchText="have asked";
char [] split=new char[]{',',' ','.'};
var splitSentence=sentence.ToLower().Split(split);
var splitText=searchText.ToLower().Split(split);
Console.WriteLine("Search Sentence {0}",splitSentence.Length);
Console.WriteLine("Search Text {0}",splitText.Length);
var count=0;
for(var i=0;i<splitSentence.Length;i++){
if(splitSentence[i]==splitText[0]){
var index=i;
var found=true;
var j=0;
for( j=0;j<splitText.Length;j++){
if(splitSentence[index++]!=splitText[j])
{
found=false;
break;
}
}
if(found){
Console.WriteLine("Index J {0} ",j);
count++;
i= index >i ? index-1 : i;
}
}
}
Console.WriteLine("Total found {0} substring",count);
可能的解决方案是使用Regex：
var count = Regex.Matches(input.ToLower(), String.Format("\b{0}\b", "the")).Count;
您可以使用while循环搜索第一次出现的索引，然后从找到的索引++位置进行搜索并在循环结束时设置一个计数器。循环变为直到索引== -1。
那么问题不是你想的那么简单;应该注意许多问题，例如标点符号，字母大小写以及如何识别字边界等问题。但是，使用N_Gram概念我提供以下解决方案：
1-确定密钥中有多少个单词。将其命名为N.
2-提取文本中所有N个连续的单词序列（N_Grams）。
3-计算N_Grams中键的出现次数
string text = "I have asked the question in StackOverflow. Therefore i can expect answer here.";
string key = "the question";
int gram = key.Split(' ').Count();
var parts = text.Split(' ');
List<string> n_grams = new List<string>();
for (int i = 0; i < parts.Count(); i++)
{
if (i <= parts.Count() - gram)
{
string sequence = "";
for (int j = 0; j < gram; j++)
{
sequence += parts[i + j] + " ";
}
if (sequence.Length > 0)
sequence = sequence.Remove(sequenc.Count() - 1, 1);
n_grams.Add(sequence);
}
}
// The result
int count = n_grams.Count(p => p == key);
}
例如，对于key = the question并将single space视为单词边界，将提取以下bi-gram：
我有 问过了 问道 这个问题 问题 在StackOverflow中。 堆栈溢出。因此 因此我 我可以 可以期待 期待答案 回答这里。
并且the question出现在文本中的次数并不明显：1
此解决方案应该在字符串所在的任何位置都能
var str = "I have asked the question in StackOverflow. Therefore i can expect answer here.";
var numMatches = Regex.Matches(str.ToUpper(), "THE")
.Cast<Match>()
.Count(match =>
(match.Index == 0 || str[match.Index - 1] == ' ') &&
(match.Index + match.Length == str.Length ||
!Regex.IsMatch(
str[match.Index + match.Length].ToString(),
"[a-zA-Z]")));
string input = "I have asked the question in StackOverflow. Therefore i can expect answer here.";
string pattern = @"\bthe\b";
var matches = Regex.Matches(input, pattern, RegexOptions.IgnoreCase);
Console.WriteLine(matches.Count);
见Regex Anchors - “\ b”。
试试这样吧
string Text = "I have asked the question in StackOverflow. Therefore i can expect answer here.";
Text = Text.ToLower();
Dictionary<string, int> frequencies = null;
frequencies = new Dictionary<string, int>();
string[] words = Regex.Split(Text, "\\W+");
foreach (string word in words)
{
if (frequencies.ContainsKey(word))
{
frequencies[word] += 1;
}
else
{
frequencies[word] = 1;
}
}
foreach (KeyValuePair<string, int> entry in frequencies)
{
string word = entry.Key;
int frequency = entry.Value;
Response.Write(word.ToString() + "," + frequency.ToString()+"</br>");
}
要搜索特定的单词然后尝试像这样。
string Text = "I have asked the question in StackOverflow. Therefore the i can expect answer here.";
Text = Text.ToLower();
string searchtext = "the";
searchtext = searchtext.ToLower();
string[] words = Regex.Split(Text, "\\W+");
foreach (string word in words)
{
if (searchtext.Equals(word))
{
count = count + 1;
}
else
{
}
}
Response.Write(count);