Primary Clustering Primary clustering is the tendency for a collision resolution scheme such as linear probing to create long runs of filled slots near the hash position of keys. If the primary hash index is x, subsequent probes go to x+1, x+2, x+3 and so on, this results in Primary Clustering. Once the primary cluster … Read more
For anybody still looking for this information. There is a WebCrypto API which appears to have been finalised at the beginning of 2017. To use it in a browser, you can find it at window.crypto.subtle which contains methods for encryption, digests etc. Documentation on the available functions here.
Hash-tables could not claim “amortized constant time insertion” if, for instance, the resizing was by a constant increment. In that case the cost of resizing (which grows with the size of the hash-table) would make the cost of one insertion linear in the total number of elements to insert. Because resizing becomes more and more … Read more
Yes, building hash sets that way is a common idiom. Note that: my @keys = qw/a b c d/; my %hash; @hash{@keys} = (); is preferable to using 1 as the value because undef takes up significantly less space. This also forces you to uses exists (which is the right choice anyway).
Most uses of SHA-1 are for interoperability: we use SHA-1 when we implement protocols where SHA-1 is mandated. Ease of development also comes into account: SHA-1 implementations in various languages and programming environment are more common than SHA-512 implementations. Also, even so most usages of hash functions do not have performance issues (at least, no … Read more
Why don’t you just truncate SHA1 or MD5? You’ll have more collisions then if you didn’t truncate, but it’s still better than designing your own. Note that you can base64-encode the truncated hash, rather than using hexadecimal. E.g. import base64 import hashlib hasher = hashlib.sha1(“The quick brown fox”) base64.urlsafe_b64encode(hasher.digest()[:10]) You can truncate as little (including … Read more
It’s a great practice to have the trailing comma. Larry added it because he saw programmers add elements to a list (or whatever their language called it) but forget the separator character. Perl allows the trailing comma to make that less common. It’s not a quirk or side effect of something else. That’s what Perl … Read more
Try: Hash[h.sort.reverse] This should return what you want. Edit: To do it by value: Hash[h.sort_by{|k, v| v}.reverse]
You can make elem contain the value by splitting it up in 2 variables: H.reduce(0) {|memo, (key, val)| memo + val}
This is the category I use: NSString+MD5.h @interface NSString (MD5) – (NSString *)MD5String; @end NSString+MD5.m #import <CommonCrypto/CommonDigest.h> @implementation NSString (MD5) – (NSString *)MD5String { const char *cStr = [self UTF8String]; unsigned char result[CC_MD5_DIGEST_LENGTH]; CC_MD5( cStr, (CC_LONG)strlen(cStr), result ); return [NSString stringWithFormat: @”%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X”, result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7], result[8], result[9], result[10], result[11], result[12], … Read more