hash实现--开放寻址方式

来源：互联网发布：加湿器推荐知乎编辑：程序博客网时间：2024/06/05 02:42

原文：http://blog.csdn.net/aa2010aa/article/details/4908113

今天看了一下《算法导论》第十一章的散列表，里面有一节是关于开发寻址方式。

下面是我的简单的实现：

static const int __stl_num_primes = 28;static const unsigned long __stl_prime_list[__stl_num_primes] ={  53,         97,           193,         389,       769,  1543,       3079,         6151,        12289,     24593,  49157,      98317,        196613,      393241,    786433,  1572869,    3145739,      6291469,     12582917,  25165843,  50331653,   100663319,    201326611,   402653189, 805306457,   1610612741, 3221225473ul, 4294967291ul};unsigned int m = __stl_prime_list[0];int Hash_Key(int key){return key % m;}int Hash_Key1(int key){return 1 + key % (m-1);}/* int Hash_Key(int key, int i){return (Hash_Key(key) + i) % m;} */int Hash_Key(int key, int i){return (Hash_Key(key) + i * Hash_Key1(key)) % m;}int Hash_Create(int *&hashTable){if(0 == m){hashTable = NULL;return -1;}hashTable = new int[m];if (NULL == hashTable){return -1;}for(unsigned int i = 0; i < m; i++)hashTable[i] = -1;return 1;}int Hash_Insert(int *hashTable, int value){int key = Hash_Key(value, 0);for(unsigned int i = 1; i < m; i++){if (-1 == hashTable[key]){hashTable[key] = value;return key;}key = Hash_Key(value, i);}return -1;}int Hash_Find(int *hashTable, int value){int key = Hash_Key(value, 0);for(unsigned int i = 1; i < m; i++){if(-1 == hashTable[key]){return -1;}if(value == hashTable[key]){return key;}key = Hash_Key(value, i);}return -1;}void Hash_Delete(int *hashTable){delete []hashTable;}

下面是测试：

int main(){srand(time(NULL));unsigned int k;unsigned int i;clock_t begin, finish;cin >> k;for(i = 0; i < __stl_num_primes && k > __stl_prime_list[i]; i++);m = __stl_prime_list[i];int  *hap;try{Hash_Create(hap);}catch(bad_alloc &e){cout << "create wrong" << endl;return -1;}begin = clock();for(unsigned int i = 0; i < m / 10; i++){int d = Random32()%m;if( -1  == Hash_Insert(hap, d)){cout << "insert wrong" << endl;}}finish = clock();cout << "insert time";cout << (double)(finish - begin)/CLOCKS_PER_SEC << endl;begin = clock();for(unsigned int i = 0; i < m / 10; i++){int d = Random32()%m;if( -1  == Hash_Find(hap, d)){//cout << d << "  find wrong" << endl;}}finish = clock();cout << (double)(finish - begin)/CLOCKS_PER_SEC << endl;Hash_Delete(hap); }

其中的Random32（）的实现是：

unsigned int Random32(void) {             static const unsigned long x[55] = {         1410651636UL, 3012776752UL, 3497475623UL, 2892145026UL, 1571949714UL,         3253082284UL, 3489895018UL, 387949491UL, 2597396737UL, 1981903553UL,         3160251843UL, 129444464UL, 1851443344UL, 4156445905UL, 224604922UL,         1455067070UL, 3953493484UL, 1460937157UL, 2528362617UL, 317430674UL,         3229354360UL, 117491133UL, 832845075UL, 1961600170UL, 1321557429UL,         747750121UL, 545747446UL, 810476036UL, 503334515UL, 4088144633UL,         2824216555UL, 3738252341UL, 3493754131UL, 3672533954UL, 29494241UL,         1180928407UL, 4213624418UL, 33062851UL, 3221315737UL, 1145213552UL,         2957984897UL, 4078668503UL, 2262661702UL, 65478801UL, 2527208841UL,         1960622036UL, 315685891UL, 1196037864UL, 804614524UL, 1421733266UL,         2017105031UL, 3882325900UL, 810735053UL, 384606609UL, 2393861397UL };       static int init = 1;       static unsigned long y[55];       static int j, k;       unsigned long ul;           if (init)       {         int i;               init = 0;         for (i = 0; i < 55; i++) y[i] = x[i];         j = 24 - 1;         k = 55 - 1;       }           ul = (y[k] += y[j]);       if (--j < 0) j = 55 - 1;       if (--k < 0) k = 55 - 1;       return((unsigned int)ul);   }

c函数rand（）产生的数在0~RAND_MAX之间（在我的机器，RAND_MAX的大小是32767），比较小，不利于测试，Random32函数

能产生0到unsigned int最大之间的数。

开放寻址的方式相对链表方式节省了空间（省了一个指针），但加大了插入和查找时间，特别如果插入的数重复太多的话，那么时间会有一个很大的提升。

下面是测试结果：

如果用rand代替Random32，测试结果是：

当到了10000000，对比一下就知道，那时间是花花的上去了。

0 0