c++ - vector iterating over itself -


in project have vector wit relational data (a struct holds 2 similar objects represent relationship between them) , need check relationships combinations between data in vector.

what doing iterating on vector , inside first loop iterating again relationships between data.

this simplified model of doing

for(a=0; a<vec.size(); a++) {     for(b=0; b<vec.size(); b++)     {         if(vec[a].something==vec[b].something) {...}     } }

my collection has 2800 elements means iterating 2800*2800 times...

what kind of data structure more suitable kind of operation? using for_each faster traversing vector this?

thanks in advance!

vec has 2 structs made of 2 integers , nothing ordered.

no, for_each still same thing.

using hash map make problem better. start empty hash , iterate through list. each element, see if it's in hash. if it's not, add it. if is, have duplicate , run code.

in c++, can use std::map. in c, there no built in map datastructure, you'd have make own.

the high-level pseudo code this

foreach (element in array)   if map.has_key(element)     do_stuff(element)   else     map.add_key(element)

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