由字符串而不是整数值索引的矩阵

Question

Is it possible in C++ to have a matrix of int values where I can access to these values through string indexes ? Doing something like M["one"]["two"]++; etc.

Answer 1

Use unordered_map (in boost or c++11 ) or just map in good old C++ . Make a unordered_map<string, unordered_map<string, int> > . Should do the trick.

Answer 2

It's not direct, but since you ask, you probably don't know about operator []() . You can define your custom [] operator.

Just to explain you the concept behind: you could define a class Row, or Column, owning a std::vector<int> . For this class you could define the operator[] :

class Row
{
public:
    int& operator[](const std::string& );
    //...
    std::vector<int> ints;
}

Your class matrix then would own a std::vector<Row>

class Matrix
{
public:
    Row& operator[](const std::string& );
    //...
    std::vector<Row> rows;
}

this would enable you to use the syntax Matrix m; m["one"]["two"]=2; Matrix m; m["one"]["two"]=2;

Answer 3

I would keep internal details separate from the user interface.

What if you want to use a different language, for example?

Have a map from the word to the integer:

map<string, unsigned int> index;
index["one"] = 1;
// .etc

Use the integer on a 2D array, as normal.

int x = index["one"];
int y = index["two"];

doSomething(array[x][y]);