良好的字符串散列函数 [英] Good Hash Function for Strings

问题描述

我试图想出一个很好的字符串散列函数。我认为总结字符串中前五个字符的unicode值可能是个好主意（假设它有五个字符，否则停止它的结束位置）。这是一个好主意，还是一个坏的？

I'm trying to think up a good hash function for strings. And I was thinking it might be a good idea to sum up the unicode values for the first five characters in the string (assuming it has five, otherwise stop where it ends). Would that be a good idea, or is it a bad one?

我在Java中这样做，但我不会想象这会有很大的不同。

I am doing this in Java, but I wouldn't imagine that would make much of a difference.

推荐答案

通常哈希不会执行和，否则 stop 和 pots 将具有相同的散列。

Usually hashes wouldn't do sums, otherwise stop and pots will have the same hash.

并且您不会将其限制为前n个字符，房屋将具有相同的散列。

and you wouldn't limit it to the first n characters because otherwise house and houses would have the same hash.

通常，散列值取值并将其乘以一个素数（使其更容易产生独特的散列）。因此，您可以执行如下操作：

Generally hashs take values and multiply it by a prime number (makes it more likely to generate unique hashes) So you could do something like:

int hash = 7;
for (int i = 0; i < strlen; i++) {
    hash = hash*31 + charAt(i);
}

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