NSSortDescriptor *frequencyDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"" ascending:NO comparator:^(id obj1, id obj2) { return [obj1 compare:obj2 options:NSNumericSearch]; }];

NSEnumerator * enumerator = [arr_distance objectEnumerator];

NSArray * descriptors = [NSArray arrayWithObjects:frequencyDescriptor, nil];

NSArray * sortedArray = [arr_distance sortedArrayUsingDescriptors:descriptors];

enumerator = [sortedArray objectEnumerator];

NSLog(@"sortedArray = %@",sortedArray);