Though CFArray comes with binary search capability, NSArray does not โ at least not within the iPhone SDK. The indexOfObject:inSortedRange:options:usingComparator: can’t be found.
Plus the CFArrayBSearchValues doesn’t tell you whether the key actually is part of the list or not. That’s what the Java JDK does, so let’s implement some category methods
-(NSInteger)binarySearch:(id)key;
-(NSInteger)binarySearch:(id)key usingSelector:(SEL)comparator;
-(NSInteger)binarySearch:(id)key usingSelector:(SEL)comparator inRange:(NSRange)range;
-(NSInteger)binarySearch:(id)key usingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context;
-(NSInteger)binarySearch:(id)key usingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context inRange:(NSRange)range;
-(NSInteger)binarySearch:(id)key usingDescriptors:(NSArray *)sortDescriptors;
-(NSInteger)binarySearch:(id)key usingDescriptors:(NSArray *)sortDescriptors inRange:(NSRange)range;
ourselves, like
-(NSInteger)binarySearch:(id)key usingFunction:(NSInteger (*)(id, id, void *))comparator context:(void *)context inRange:(NSRange)range
{
NSLogD(@"[NSArray(MroBinarySearch) binarySearch:%@ usingFunction:]", key);
if(self.count == 0 || key == nil || comparator == NULL)
return [self binarySearch:key usingSelector:nil inRange:range];
// check overflow?
NSInteger min = range.location;
NSInteger max = range.location + range.length - 1;
while (min <= max)
{
// http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html
const NSInteger mid = min + (max - min) / 2;
switch (comparator(key, [self objectAtIndex:mid], context))
{
case NSOrderedSame:
return mid;
case NSOrderedDescending:
min = mid + 1;
break;
case NSOrderedAscending:
max = mid - 1;
break;
}
}
return -(min + 1);
}
See the full interface + implementation + testcase without html encoding dirt at github.