how to add an element to an array in c++?

Question

How would I add an element to an array, assuming that I have enough space? My code looks something like this:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main(){
    ofstream out("hi.out");
    ifstream in("hi.in");
    string currentLine;
    string values[135];/*Enough for worst case scenario*/
    if (out.is_open && in.isopen()){
        while (in >> currentLine){
            /*Add currentLine to values*/
        }
        /*Do stuff with values and write to hi.out*/
    }
    out.close()
    in.close()
    return 0;
}

Don't. Use a vector.

Lightness Races in Orbit
– Lightness Races in Orbit

2015-09-14 22:09:34 +00:00
Commented Sep 14, 2015 at 22:09 — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Sep 14, 2015 at 22:09

T.C. · Accepted Answer · 2015-09-15 10:07:32Z

4

No need to write the loop yourself. With your array:

auto l = std::copy(std::istream_iterator<std::string>(in), {}, values);

l - values is the number of strings read.

Or even better, use a vector, so that you don't have to worry about the possibility of your "worst case scenario" not being the actual worst case scenario.

std::vector<std::string> values(std::istream_iterator<std::string>(in), {});

edited Sep 15, 2015 at 10:07

answered Sep 14, 2015 at 22:13

T.C.

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1 Comment

clamchowder314 Over a year ago

I am not really that good at C++, could you explain more to me what this does?

owacoder · Accepted Answer · 2015-09-14 22:20:08Z

1

You could use an index counter variable:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main(){
    ofstream out("hi.out");
    ifstream in("hi.in");
    string currentLine;
    string values[135];/*Enough for worst case scenario*/
    int index = 0;
    if (out.is_open && in.isopen()){
        while (in >> currentLine){
            /*Add currentLine to values*/
            values[index++] = currentLine;
        }
        /*Do stuff with values and write to hi.out*/
    }
    out.close()
    in.close()
    return 0;
}

The variable index, once the loop is complete, will contain the number of strings in your array.

edited Sep 14, 2015 at 22:20

answered Sep 14, 2015 at 22:13

owacoder

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