Save words of a file in a vector of string

Question

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I wrote:

void contare()

{
	
vector <string> va;

fstream fs;

int n=0;

char ch;
		
fs.open("C:\\Users\\Mio\\Desktop\\ciao.txt",ios::in);

while (! fs.eof())

{
 	ch = fs.get();
 	
 	cout<<ch;
 	
va[n] += ch;
 
if (ch== ' ')
 n++;


}


fs.close();

cout<<n;
	

  //cout<<worda<<endl;
}

What I have tried:

but it doesn't work, when I wrote in vectore there is a block, have you have some ideas?

Posted 28-Oct-19 4:41am

Member 14594285

Updated 28-Oct-19 5:01am

v2

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Comments

Patrice T 28-Oct-19 10:48am

What is a "block" ?
Describe the problem

Member 14594285 28-Oct-19 10:54am

in my file there is written:
"ciao ciao ciao"

program prints only "c"

2 solutions

Solution 1

Hi Valentina, there is no need to explicitely handle file opening/closing. You could make the program accepting input from standard in and then redirect the intended file on program call. e.g.

my_program < my_input_file

Also, there is no need to explicitely find word boundaries, cin can gently do such a job for you.
Try

C++

#include <iostream>
#include <vector>
using namespace std;

int main()
{
  vector <string> vw; // vector of 'words'

  while (true)
  {
    string word;
    cin >> word;
    if ( ! cin ) break;
    vw.push_back(word);
  }

  cout << "count of words is " << vw.size();
}

Posted 28-Oct-19 4:59am

CPallini

Comments

Member 14594285 28-Oct-19 11:03am

yes but in this way I write always in a string, I wanto yo write only a word in vw[0], vw[1]...ecc..

k5054 28-Oct-19 11:23am

Why make things more complicated than they have to be? Still, if you insist then:

string s;
while( !fs.eof() ) {
    ch = fs.get();
    if(ch == ' ') {
       v.push_back(s);
       s.erase();
    } else {
       s += ch;
    }
}

Note that both CPallini and I have given very similar answers, so that might be a clue how an experienced developer might approach the problem. You might want to think about why you want to read a single char at a time. Note that for large files, reading single characters at a time may be significantly slower than reading word by word.

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k5054 · Accepted Answer · 2019-10-28T05:01:00

Solution 2

Unlike arrays, vectors have no fixed length. When you define a vector as vector<type> v, it has an initial length of zero. That means that if you try to reference any vector element, you will most likely get a program crash due to attempting to access unassigned memory. In general you want to use vector.push_back() to add elements to the end of a vector.

Try this

C++

ifstream ifile("myfile.txt");
vector<string> words;
string word;
while(ifile >> word) {
    words.push_back(word);
}

Posted 28-Oct-19 5:01am

k5054

Comments

Member 14594285 28-Oct-19 11:30am

I wote:
void contare(vector<string> words)

{
ifstream ifile("C:\\Users\\Mio\\Desktop\\ciao.txt");

string word;

while(ifile >> word)
{
words.push_back(word);
}

}

int main()
{
vector<string> words;

contare(words);

but it doesn't works when I pass wors to contare

k5054 28-Oct-19 11:40am

C++ uses "pass by value" by default. That means that when you have

void foo(vector<string> words)
{
   ...
}
int main()
{
    vector<string> v;
    foo(v);
}

the call to foo() creates a copy of vector v, passes that to foo(). When foo() returns, the copy is destroyed. What you want to do is use pass by reference. Look up references in C++.

CPallini 28-Oct-19 11:48am

Then write:
vector <string> contare()
{
ifstream ifile("C:\\Users\\Mio\\Desktop\\ciao.txt");

string word;
vector <string> words;
while(ifile >> word)
{
words.push_back(word);
}
return words;
}

and call it this way:
int main()
{
vector<string> words = contare();
//...

Member 14594285 28-Oct-19 12:23pm

thanks a lot, I solved