Is it me? I must be a little slow. I've just noticed something, and I made a little program that demonstrates my point:

Sorry if it's a little messy.Code:#include <iostream> #include <cstddef> int *binary_search( int list[], std::size_t length, int value ) { std::size_t hi_end = length - 1, low_end = 0, midpoint; while( low_end <= hi_end ) { midpoint = low_end + (hi_end - low_end) / 2; if( value == list[midpoint] ) return &list[midpoint]; else if( value < list[midpoint] ) hi_end = midpoint - 1; else low_end = midpoint + 1; } return NULL; } int main( ) { int *series = NULL; std::size_t length = 0; std::cout <<"Enter a length for the series:\n"; std::cin >>length; if( length > 0 ) { series = new int[length]; if( series ) { for( std::size_t i = 0; i < length; i++ ) series[i] = static_cast< int >( i + 1 ); int find_it = 0; std::cout <<"Enter a search item:\n"; std::cin >>find_it; int *match = binary_search( series, length, find_it ); if( match ) std::cout <<"Found a match for " <<*match <<".\n"; else std::cout <<"Sorry, no match.\n"; delete[] series; } else { std::cout <<"Failed to allocate space for the series.\n"; } } else { std::cout <<"Invalid length value. Try again.\n"; } }

Anyway, I wrote that earlier today and realized that if I tried to search for 0 in a list of 2 or more elements, it breaks horribly, but not all the time. If you put a negative number in there then binary search is happy again and can return a failed search without crashing the program.

I figured out why it crashes at least. hi_end eventually underflows and causes problems. But the real question is if I have cause to be concerned. It seems silly that you can't search for zero amongst a list of positive integers, risking failure. What do smart people do?