C++ Find Word in String without Regex - c++

Question

I'm trying to find a certain word in a string, but find that word alone. For example, if I had a word bank:
789540132143
93
3
5434
I only want a match to be found for the value 3, as the other values do not match exactly. I used the normal string::find function, but that found matches for all four values in the word bank because they all contain 3.
There is no whitespace surrounding the values, and I am not allowed to use Regex. I'm looking for the fastest implementation of completing this task.

Answer 1

If you want to count the words you should use a string to int map. Read a word from your file using >> into a string then increment the map accordingly
string word;
map<string,int> count;
ifstream input("file.txt");
while (input.good()) {
input >> word;
count[word]++;
}
using >> has the benefit that you don't have to worry about whitespace.

Answer 2

All depends on the definition of words: is it a string speparated from others with a whitespace ? Or are other word separators (e.g. coma, dot, semicolon, colon, parenntheses...) relevant as well ?
How to parse for words without regex:
Here an accetable approach using find() and its variant find_first_of():
string myline; // line to be parsed
string what="3"; // string to be found
string separator=" \t\n,;.:()[]"; // string separators
while (getline(cin, myline)) {
size_t nxt=0;
while ( (nxt=myline.find(what, nxt)) != string::npos) { // search occurences of what
if (nxt==0||separator.find(myline[nxt-1])!=string::npos) { // if at befgin of a word
size_t nsep=myline.find_first_of(separator,nxt+1); // check if goes to end of wordd
if ((nsep==string::npos && myline.length()-nxt==what.length()) || nsep-nxt==what.length()) {
cout << "Line: "<<myline<<endl; // bingo !!
cout << "from pos "<<nxt<<" to " << nsep << endl;
}
}
nxt++; // ready for next occurence
}
}
And here the online demo.
The principle is to check if the occurences found correspond to a word, i.e. are at the begin of a string or begin of a word (i.e. the previous char is a separator) and that it goes until the next separator (or end of line).
How to solve your real problem:
You can have the fastest word search function: if ou use it for solving your problem of counting words, as you've explained in your comment, you'll waste a lot of efforts !
The best way to achieve this would certainly be to use a map<string, int> to store/updated a counter for each string encountered in the file.
You then just have to parse each line into words (you could use find_fisrst_of() as suggested above) and use the map:
mymap[word]++;