4-1 LC：二分查找

有序数组的二分查找

NSInteger GetIndexInArr(NSArray *arr,NSNumber *num) {
    NSInteger min = 0;
    NSInteger max = arr.count - 1;
    NSInteger mid = 0;
    
    while (min <= max) {
        mid = (min + max) / 2;
        if ([arr[mid] integerValue] == num.integerValue) {
            return mid;
        } else if ([arr[mid] integerValue] > num.integerValue) {
            max = mid - 1;
        } else {
            min = mid + 1;
        }
    }
    
    return -1;
}