This task is quite common task. However, explicit insertion of values can be unacceptable in many cases?like if you need to insert a lot of values.

I’ve found that it’s quite handy to use arrays for this task:

 pair arr[] ={   pair("640x480", 0),   pair("800x600", 1),   pair("1024x800", 2),   pair("1280x1024", 3)};map msi(arr, arr + sizeof(arr)/sizeof(arr[0]));

This technique is easily applied to vectors, sets, etc.