哈希方法

字符串处理：

unix的ELF哈希函数

unsigned int ELFHash(char* str)
{
    unsigned int hash = 0;
    unsigned int x = 0;

    while (*str){
        hash = (hash << 4) + (*str++);
        if ((x = hash & 0xF0000000L) != 0){
            hash ^= (x >> 24);
            hash &= ~x;
        }
    }
    return (hash & 0x7FFFFFFF);
}

　　

BKDRHash 哈希

unsigned int BKDRHash(char * str)  
{  
    unsigned int seed = 31;//31 131 1313 13131  
    unsigned int key = 0;  
    while (*str)  
        key = key*seed+ *str++;  
    return key&(0x7fffffff);  
}  

　　

开散列：

挂链实现：

void Gua(int tmp){
    int tp = tmp%N;
    if (tp < 0) tp = -tp;
    node *t = &H[pos++];
    t->num = tmp;
    t->next = tagp[tp];
    tagp[tp] = t;
}
int Cha(int tmp){
    int tp = tmp%N;
    if (tp < 0) tp = -tp;
    node *q;
    int count = 0;
    for (q = tagp[tp]; q != NULL; q = q->next){
        if (q->num == tmp) count++;
    }
    return count;
}

　　

　　

vector<>实现：

vector<int>hash[N];
void Gua(int tmp){
    int tp = tmp%N;
    if (tp < 0) tp = -tp;
    hash[tp].push_back(tmp);
}
int Cha(int tmp){
    int tp = tmp%N;
    if (tp < 0) tp = -tp;
    int count = 0,k;
    int sz = hash[tp].size();
    for (k = 0; k < sz; ++k){
        if (hash[tp][k] == tmp) count++;
    }
    return count;
}