使用C ++ STL的多维矢量解

Question

I Would like to try the below mentioned implementation using C++ STL. My requirement is to create a Matrix mentioned below. The string of vectors are :

Basically i would want to update the matrix counting the no of Man/woman/kids. For eg Based on the Sample Input mentioned below ,expected output is: For Tokyo => Man=1, Woman=1, Kid=0 .

The approach I think is to first sort the Cities and get the unique values. and then similarly do it for Man, Woman & Kids. Then count the no of Man/Woman/kids for that city. To do this which kind of container would be ideal, ordered map ? How should i handle such multidimensional array problems. What would be the most efficient way to handle this kind of situation.Any other solution would be highly appreciated.

Sample Input

Expected Output [ will be filled accordingly, please ignore empty fields]

Answer 1

It depends whether the possible values of any dimensions are know a priori or not. If they are, a simple array will be the best container, else you should use a map. If order does not matter, use an unordered_map , if you can sort it, use an ordered map , and if you want to keep input order, use a list where the indexes are stored in a map.

If the categories are known to get only 3 possible values (Man, Woman, Kid) and the cities are not known a priori, I would use:

std::map<std::string, std::array<int, 3> > resul;

std::string town, cat;
for(;;) {
    std::cin >> town >> cat;
    if (! std::cin) break;
    if (resul.find(town) == resul.end()) {
        resul[town].fill(0);
    }
    std::array<int, 3>& curtown = resul[town];
    if (cat == "Man") curtown[MAN] += 1;
    else if (cat == "Woman") curtown[WOMAN] += 1;
    else curtown[KID] += 1;
}