Question

I am looking for a way to “zip” a multikey map to a normal map. My multimap looks like this:

Key                 v a l u e s 
<string>            <string>

140,1,08,2500       1456 
140,1,10,3040       1456 
.............       ....
.............       ....
140,1,08,2500       8g   
140,1,13,3040       8g   
.............       ....

The first and the penultimate key are identical. My goal is to merge these two (and all other duplicate key pairs) lines so that the result is:

140,1,08,2500       14568g

The values belonging to the original two keys being merged. Now, I could write some nice loop and iterate and copy and delete stuff and so on, but I wonder if anyone knows a smart, maybe even fast way to get this done.

Answer 1

Keep it simple…

map<string, string> new_map;

for(auto it = mmap.begin(), end = mmap.end(); it != end; ++it)
{
  new_map[it->first].append(it->second);
}

Why make it more complicated?