c - C 中哈希码的递归

Question

我正在尝试制作哈希码函数。

但是，我得到的随机数不等于示例，我无法确定为什么(5是最大长度，所以不需要动态内存分配)

Answer 1

来自 strncpy documentation :

No null-character is implicitly appended at the end of destination if source is longer than num. Thus, in this case, destination shall not be considered a null terminated C string (reading it as such would overflow).

所以你想做的:

strncpy(new, str, l - 1);
new[l - 1] = 0;

但您也可以避免使用辅助函数创建新字符串:

unsigned long hash_helper(const char* str, int len){
    if (len == 0) return 0;
    return hash_helper(str, len - 1) * 65599 + str[len - 1]; 
}

unsigned long hash(const char* str){
    return hash_helper(str, strlen(str));
}