Is this a valid datastructure Map in C++?

Question

I have to store 3 strings per variable, but don't know which is the best data structure to use for that in C++.
I can think of only Struct, but not sure if it is the best way to do it.

Something like string var[100][3], first dimension(100) should be dynamically add and remove.

I tried all sorts of things with map, multimap.

Any help is appreciated. Thank you

Your question isn't clear. Do you *always* have exactly 3, or do you want to "dynamically add and remove"? — Oliver Charlesworth, Feb 08 '11 at 15:12
could you give an example of key/values you are storing to make it a little clearer what you need? — Jordan, Feb 08 '11 at 15:19

score 8 · Accepted Answer · answered Feb 08 '11 at 15:14

8

If you have always exactly 3 strings together in a triplet and want to have multiple triplets, then define struct with three strings and put it to std::vector.

struct Triplet {
  std::string a,b,c;
};

std::vector<Triplet> data;

answered Feb 08 '11 at 15:14

Al Kepp

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@Ringo you could use classes too, check my answer. But this is beautiful! +1 – karlphillip Feb 08 '11 at 15:21
Yours also looks good, but what makes you think this is better than using classes? – rda3mon Feb 08 '11 at 16:19
@Ringo I said it was beautiful, not better! ;D – karlphillip Feb 08 '11 at 16:29
1

@Ringo @Al Anyway, here's an interesting debate on `Class vs Struct for data only`: http://stackoverflow.com/q/431429/176769 – karlphillip Feb 08 '11 at 16:37

score 3 · Answer 2 · answered Feb 08 '11 at 15:20

Map<string, string, string> is not valid. However, you could create a new data structure with 3 strings and store it in a vector.

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class data_structure
{
public:
    string first;
    string second;
    string third;
};


int main()
{
    vector<data_structure> my_vec;

    data_structure elem1;
    elem1.first = "one";
    elem1.second = "two";
    elem1.third = "three";

    my_vec.push_back(elem1);

    data_structure elem2;
    elem2.first = "four";
    elem2.second = "five";
    elem2.third = "six";

    my_vec.push_back(elem2);

    for (int i = 0; i < my_vec.size(); i++)
    {
        // print stuff
    }

}

Judge Maygarden · Answer 3 · 2011-02-08T15:25:18.463

If you always want 3 strings, then a tuple would require less overhead.

#include <iostream>
#include <string>
#include <tuple>

typedef std::tuple<std::string, std::string, std::string> MyTuple;

int
main(int argc, char **argv)
{
    MyTuple t =
        make_tuple(
                std::string("string 1"),
                std::string("string 2"),
                std::string("string 3")
                );

    std::cout
        << std::get<0>(t) << std::endl
        << std::get<1>(t) << std::endl
        << std::get<2>(t) << std::endl;

    return 0;
}

score 1 · Answer 4 · answered Feb 08 '11 at 15:13

1

you can use a class or a tuple, and store the tuple in a vector

std::vector<boost::tuple<std::string, std::string, std::string> > v;
boost::tuple<std::string, std::string, std::string> t = boost::make_tuple(s1, s2, s3);
v.push_back(t)

answered Feb 08 '11 at 15:13

kinnou02

644
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15

score 1 · Answer 5 · answered Feb 08 '11 at 15:21

1

Another to the above mix of suggestions: Boost Tuple (if you have Boost installed already).

answered Feb 08 '11 at 15:21

yasouser

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DVK · Answer 6 · 2011-02-08T15:18:03.410

You can use vector to store N elements

vector<string> three_strings(3);

 three_strings.push_back("one");
 three_strings.push_back("two");
 three_strings.push_back("three");

Please note that tuple is an alternative, BUT: (1) it is part of tr1 standard and therefore may not be available on your C++ compiler/installation yet; (2) It stores heterogeneous data (e.g. 3 random type items, not necessarily 3 strings) which may be an overkill

score 0 · Answer 7 · answered Feb 08 '11 at 15:14

0

Map <string , vector <string> > Will allow you to map a vector of strings to a string key value. If you have the same number of strings mapped to each key then use an array of strings to reduce the memory overhead of the vector.

answered Feb 08 '11 at 15:14

Jordan

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score 0 · Answer 8 · answered Feb 08 '11 at 15:27

0

How about vector<vector<string> > ?

answered Feb 08 '11 at 15:27

Stephen Chu

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Is this a valid datastructure Map in C++?

8 Answers8