我不知道这是什么意思的代码. [英] A code, that I do not know what it meant.

问题描述

你好.
此代码是做什么用的?
而"for"的目的是什么?

Hello.
What does this code do?
And what is the purpose of the "for" while?

int hash(const char *str) 
{
    if (str != 0)
    {
        unsigned h = str [0];
        for (int i = 1; str [i] != 0; ++i)
            h = (h << 5) - h + str [i];
        return h % HASH_SIZE; // remainder
    }
    else
    {
        return -1;
    }
}

推荐答案

这似乎是 djb2 [不同的常量 [此处 [

This seems to be the java string hashing algorithm[^]. It is a variant of the djb2[^] with different constants[^]. Here[^] you can find some explanation about the constants of djb2.

请参见此处 [ ^ ]，以及之前和之后的页面.

See here[^], and preceding and succeeding pages.

尝试提供不同的字符串作为输入并查看输出是什么.随着for循环的进行，通过代码进行调试以检查h的不同值；当然，还有h的最终值.您需要在程序的开头定义HASH_SIZE.

Try giving different strings as input and seeing what the output is. And debugging through the code to inspect the different values of h as the for loop progresses; and, of course, the final value of h. You need to define HASH_SIZE towards the beginning in the program.

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