how can I serialize 2 sets using nlohmann/json.hpp - c++

Question

I have two unordered sets of pairs (X,Y) implemented using boost hash and I would like to convert them to a Json file that has a special format.
unordered_set<pair<int,int>> visited, cleaned
. I want them to be represented this way in Json format using nlohmann/json.hpp C++:
{
"visited": [
{
"X": 2,
"Y": 2
},
{
"X": 3,
"Y": 0
},
{
"X": 3,
"Y": 1
},
{
"X": 3,
"Y": 2
}
],
"cleaned": [
{
"X": 2,
"Y": 2
},
{
"X": 3,
"Y": 0
},
{
"X": 3,
"Y": 2
}
],
}
can anyone help me with the c++ code for this part?
my code is
for (auto it = visited.begin(); it != visited.end(); ++it)
{
j2["visited"]["X"]=it->second;
j2["visited"]["Y"] = it->first;
}
for (auto it = cleaned.begin(); it != cleaned.end(); ++it)
{
j2["cleaned"]["X"] = it->second;
j2["cleaned"]["Y"] = it->first;
}
and it produces:
{
"cleaned": {
"X": 3,
"Y": 2
},
"visited": {
"X": 3,
"Y": 2
}
}

Answer 1

The JSON format you want contains arrays. Use something like this to explicitly create
them:
nlohmann::json arr;
for (auto it = visited.begin(); it != visited.end(); ++it) {
nlohmann::json o;
o["X"] = it->second;
o["Y"] = it->first;
arr.push_back(o);
}
j2["visited"] = arr;
And similarly for the second part.