Essential C++

binary_search()

Assumes that the container is sorted by the less-than operator. If the container is sorted by some other ordering relationship, the binary operator must be passed in. The algorithm returns true or false.

#include <algorithm> 
found_it = binary_search( ilist.begin(), ilist.end(), value ); 
found_it = binary_search( vec.begin(), vec.end(), value, 
                          greater<int>() );