如何在C ++中的字符串中找到完整的单词（不是它的一部分）

Question

In a C++ code, I'm trying to search for a word in a sentence but it keeps doing partial search. I want it to search only for the complete word not parts of it too, any help?

size_t kk;
string word="spo";
string sentence="seven spoons";

kk=sentence.find(word);
if (kk !=string::npos)
cout << "something" << endl;

Answer 1

It sounds like what you want is handled by the concept of word boundaries or word characters in regular expressions.

Here's a program that will return only a complete match. That is, it will only return a word if that word completely matches the exact word you're searching for. If some word in sentence has your target word as a strict substring then it will not be returned.

#include <regex>
#include <string>
#include <iostream>

int main() {
  std::string word = "spo"; // spo is a word?
  std::string sentence = "seven spoons";

  std::regex r("\\b" + word + "\\b"); // the pattern \b matches a word boundary
  std::smatch m;

  if (std::regex_search(sentence, m, r)) { // this won't find anything because 'spoons' is not the word you're searching for
    std::cout << "match 1: " << m.str() << '\n';
  }

  sentence = "what does the word 'spo' mean?";    
  if (std::regex_search(sentence, m, r)) { // this does find the word 'spo'
    std::cout << "match 2: " << m.str() << '\n';
  }
}

Or alternatively maybe you mean you want to find any word that matches a partial word you're searching for. regex can do that as well:

  std::string partial_word = "spo";
  std::regex r("\\w*" + partial_word + "\\w*"); // the pattern \w matches a word character

This produces:

match 1: spoons
match 2: spo

Answer 2

There are a bunch of options here:

a) Search for [space]WORD[space] instead of just WORD

string word="spo";
string sentence="seven spoons";
kk=sentence.find(" "+word+" ");

Note that this wont work, if your words are separated by newline characters or other white spaces.

b) Split the string into words, store them in a vector , and check if the desired word is somewhere in the vector, by using std::find .

stringstream parser(sentence);
istream_iterator<string> start(parser);
istream_iterator<string> end;

vector<string> words(start, end);
if(find(words.begin(), words.end(), word)!=words.end()) cout<<"found!";

If you're gonna search for words often, this maybe the best choice, since you can store the vector somewhere for future reference, so you don't have to split it. Also - if you want this to work, be sure to #include <algorithm> and #include <vector> .

c) Search for the word and check if isspace(string[position-1]) && isspace(string[position+wordLength])

string word="spo";
string sentence="seven spoons";
kk=sentence.find(" "+word+" ");
if(kk!=string::npos){
    if((kk==0 || isspace(sentence[kk-1])) && (kk+word.length()==sentence.length() || isspace(kk+word.length()+1)))
       cout << "found!";
}

Answer 3

Something like this :

std::size_t kk;
std::string word="spoo";
std::string sentence="seven spoons tables";

std::stringstream ss(sentence) ;
std::istream_iterator<std::string> f ;

auto it =std::find_if(  std::istream_iterator<std::string> (ss),
                        f,
                        [=](const std::string& str){
                        return str == word;
                        }
 );

if(it != f )
 std::cout << "Success" <<std::endl;

See here

Answer 4

I think the best way is to split your string using whitespace and punctuation characters as delimiters, then use std::find on the result.

#include <boost/algorithm/string.hpp>
#include <vector>
#include <string>
#include <algorithm>

int main()
{
    std::string word="spo";
    std::string sentence="seven spoons";
    std::vector<std::string> words;
    boost::split(words, sentence, boost::is_any_of("\n\t .,!?\"()"));
    auto match = std::find(begin(words), end(words), word);
    if (match != end(words))
    {
        // Found it!
    }
    else
    {
        // Not there.
    }
 }

Answer 5

string word="spo";  
string sentence="seven spoons";  

string::size_type nIndex = sentence.find( word, 0 );  
if( nIndex != string::npos )  
{  
if ((nIndex + word.length() + 1) == sentence.length())  
{  
    cout << "Found" << endl;  
}  
else  
{  
string::size_type nSpace = sentence.find( " ", nIndex );  
if (nSpace == (nIndex + word.length()))  
{  
cout << "Found" << endl;  
}  
}  
}  
else  
{  
cout << "No Match" << endl;  
}  

Answer 6

This seems to have worked.

#include <string>

/*find word in sentence and return the index of first occurrence*/
int find_whole(string sentence,string word){
    size_t pos=sentence.find(word);
    size_t offset=pos+sentence.size()+1;

    if((pos!=string::npos) && (sentence.substr(pos,offset)==word))
        return pos;
    return string::npos;
}