string pattern recognition?

[barneygumble742]

hi,

the user inputs a line of like a hundred characters into one string and i'm using getline.

what's the logically simple way to look for 5 letter words?

currently my program has a for loop inside which contains a large if statement that says:

if ( isspace(line[i-1]) && isalpha(line[i]) && isalpha(line[i+1]) && isalpha(line[i+2]) && isalpha(line[i+3]) && isalpha(line[i+4]) && isspace(line[i+5]) )

i just think that there might be a simpler string member function that would serve the same purpose if not handle it better.

thanks,
barneygumble742

[Rashakil Fol]

Uh, right. And what exactly is he supposed to do with this function, search for every possible five-character word, with spaces on both sides? And what good does searching for "of" do in the string "Professor Hoffman offs lofty offers."?

I would go with something along the lines of:

int last_nonalph = -1;
int e = str.size() + 1;
for (int i = 0; i < e; ++i) {
    if (i == e  ||  !isalpha(str[i])) {
        if (i - last_nonalph == 6) {
            /* Do whatever you want with the range (last_nonalph + 1 .. i - 1) */
        }
        last_nonalph = i;
    }
}

[Rashakil Fol]

It has nothing to do with the problem at hand.

[major_small]

if by 5 letter words you mean words that have 5 characters, all seperated by spaces, then you could use the strtok() function in a loop

http://www.cppreference.com/stdstring/strtok.html

note that won't work on lines like: "wow!! later" because that will count as two 5-letter words. what you could do, is after you find where the 5-letter word wannabe is, you could test each character with isalpha()

http://www.cppreference.com/stdstring/isalpha.html

that still doesn't guarantee that it's a real word, but it makes sure that it contains 5 characters from the alphabet (A-z).

[ILoveVectors]

i worked on several options, cause this interested me
and the code i choose to use at the end is this,
and it account for punctuation during a word
and at the end of the sentence.

#include <iostream>
#include <ctype.h>
#include <string>
#include <sstream>
#include <vector>

using namespace std;

int main()
{
	string mystring;
	string mystring2;
	string size;
	vector<string> tokens;
	vector<string>::iterator forward;
	cout << "Enter a sentence : ";
	getline(cin, mystring, '\n');
	stringstream ss(mystring);
	while(ss >> mystring2)
	{
		tokens.push_back(mystring2);
	}
	int punct = 0;
	for(forward = tokens.begin(); forward != tokens.end(); forward++)
	{
		size = *(forward);
		for(int i = 0; i != size.size()-1; i++)
		{
			if(ispunct(size[i]))
			{
				punct++;
			}
		}
		if(ispunct(size[size.size()-1]))
		{
			size.erase(size.size()-1, 1);
		}
		if((size.size()-punct) == 5)
		{
			cout << size << endl;
		}
		punct = 0;
	}
	cin.get();
	return 0;
}