How can I display the content of a map on the console?
85,487
Solution 1
Well it depends on how you want to display them, but you can always iterate them easily:
typedef map<string, list<string>>::const_iterator MapIterator;
for (MapIterator iter = mapex.begin(); iter != mapex.end(); iter++)
{
cout << "Key: " << iter->first << endl << "Values:" << endl;
typedef list<string>::const_iterator ListIterator;
for (ListIterator list_iter = iter->second.begin(); list_iter != iter->second.end(); list_iter++)
cout << " " << *list_iter << endl;
}
Solution 2
Update (Back to the future): with C++11 range-based for loops –
std::map<Key, Value> m { ... /* initialize it */ ... };
for (const auto &p : m) {
std::cout << "m[" << p.first << "] = " << p.second << '\n';
}
Solution 3
I'd try the following
void dump_list(const std::list<string>& l) {
for ( std::list<string>::const_iterator it = l.begin(); l != l.end(); l++ ) {
cout << *l << endl;
}
}
void dump_map(const std::map<string, std::list<string>>& map) {
for ( std::map<string,std::list<string>>::const_iterator it = map.begin(); it != map.end(); it++) {
cout << "Key: " << it->first << endl;
cout << "Values" << endl;
dump_list(it->second);
}
Solution 4
I'm a little off topic here...
I guess you want to dump the map content for debugging. I like to mention that the next gdb release (version 7.0) will have a built in python interpreter which will be used by the gcc libstdc++ to provide stl pretty printers. Here is an example for your case
#include <map>
#include <map>
#include <list>
#include <string>
using namespace std;
int main()
{
typedef map<string, list<string> > map_type;
map_type mymap;
list<string> mylist;
mylist.push_back("item 1");
mylist.push_back("item 2");
mymap["foo"] = mylist;
mymap["bar"] = mylist;
return 0; // stopped here
}
which results in
(gdb) print mymap
$1 = std::map with 2 elements = {
["bar"] = std::list = {
[0] = "item 1",
[1] = "item 2"
},
["foo"] = std::list = {
[0] = "item 1",
[1] = "item 2"
}
}
Yay!
Solution 5
Another form, using <algorithm>
:
void printPair(const pair<string, list<string> > &p)
{
cout << "Key: " << p.first << endl;
copy(p.second.begin(), p.second.end(), ostream_iterator<string>(cout, "\n"));
}
for_each(mapex.begin(), mapex.end(), printPair);
Test program:
#include <iostream>
#include <map>
#include <list>
#include <iterator>
#include <algorithm>
using namespace std;
void printPair(const pair<string, list<string> > &p)
{
cout << "Key: " << p.first << endl;
copy(p.second.begin(), p.second.end(), ostream_iterator<string>(cout, "\n"));
}
int main()
{
map<string, list<string> > mapex;
list<string> mylist1;
mylist1.push_back("item 1");
mylist1.push_back("item 2");
mapex["foo"] = mylist1;
list<string> mylist2;
mylist2.push_back("item 3");
mylist2.push_back("item 4");
mylist2.push_back("item 5");
mapex["bar"] = mylist2;
for_each(mapex.begin(), mapex.end(), printPair);
}
Author by
Cute
Updated on March 22, 2020Comments
-
Cute about 4 years
I have a
map
declared as follows:map < string , list < string > > mapex ; list< string > li;
How can I display the items stored in the above map on the console?