Need efficient way to use map to store multiple values against one key

[prasadzambare]

Hi All,

I want to store multiple values against a key. Once stored I may need to search or sort the map based on the values. I want to know the efficient way to do this.

for e.g.

Want to store 3 fields in a map say City, District and Population.
And sort map by population or districy in descending order.


Please let me know your views.

[hamsterman]

To store multiple values against one key you would do

struct Val{
   int x;
   string y;
   float z[50];
};
map<string, Val> my_map;

Though note that you cannot change what the key is. And the map is already sorted by key.

If you do need to change keys, you could try http://www.boost.org/doc/libs/1_48_0/libs/multi_index/doc/tutorial/basics.html#multiple_sort (I think. I've never used it myself), or you could build a similar thing yourself using vector<Val> and binary search functions from <algorithm>.