数据结构8-哈希表

数据结构8-哈希表

1. 动态分配内存方式：

#include 
#include 

#define SIZE 20

struct DataItem {
   int data;   
   int key;
};

struct DataItem* hashArray[SIZE]; 
struct DataItem* dummyItem;
struct DataItem* item;

//获取键值
int hashCode(int key) {
   return key % SIZE;
}

//查找
struct DataItem *search(int key) {
   //get the hash 
   int hashIndex = hashCode(key);  
	
   //move in array until an empty 
   while(hashArray[hashIndex] != NULL) {
	
      if(hashArray[hashIndex]->key == key)
         return hashArray[hashIndex]; 
			
      //go to next cell
      ++hashIndex;
		
      //wrap around the table
      hashIndex %= SIZE;
   }        
	
   return NULL;        
}

//插入
void insert(int key,int data) {

   struct DataItem *item = (struct DataItem*) malloc(sizeof(struct DataItem));
   item->data = data;  
   item->key = key;

   //get the hash 
   int hashIndex = hashCode(key);

   //move in array until an empty or deleted cell
   while(hashArray[hashIndex] != NULL && hashArray[hashIndex]->key != -1) {
      //go to next cell
      ++hashIndex;
		
      //wrap around the table
      hashIndex %= SIZE;
   }
	
   hashArray[hashIndex] = item;
}

//删除
struct DataItem* delete(struct DataItem* item) {
   int key = item->key;

   //get the hash 
   int hashIndex = hashCode(key);

   //move in array until an empty
   while(hashArray[hashIndex] != NULL) {
	
      if(hashArray[hashIndex]->key == key) {
         struct DataItem* temp = hashArray[hashIndex]; 
			
         //assign a dummy item at deleted position
         hashArray[hashIndex] = dummyItem; 
         return temp;
      }
		
      //go to next cell
      ++hashIndex;
		
      //wrap around the table
      hashIndex %= SIZE;
   }      
	
   return NULL;        
}

//打印全部
void display() {
   int i = 0;
   for(i = 0; i < SIZE; i++) {
      if(hashArray[i] != NULL && hashArray[i]->key != -1) {
         printf(" (%d,%d)",hashArray[i]->key,hashArray[i]->data);
      } else {
         printf(" ~~ ");
      }
   }
   printf("\n");
}
//主函数
int main() {
   dummyItem = (struct DataItem*) malloc(sizeof(struct DataItem));
   dummyItem->data = -1;  
   dummyItem->key = -1; 

   insert(1, 20);
   insert(2, 70);
   insert(42, 80);
   insert(4, 25);
   insert(12, 44);
   insert(14, 32);
   insert(17, 11);
   insert(13, 78);
   insert(37, 97);
   insert(21, 88);

   display();
   item = search(37);

   if(item != NULL) {
      printf("Element found: %d\n", item->data);
   } else {
      printf("Element not found\n");
   }

   delete(item);
   item = search(37);

   if(item != NULL) {
      printf("Element found: %d\n", item->data);
   } else {
      printf("Element not found\n");
   }
   
   item = search(1);
   printf("Element found: %d\n", item->data);
   
   item = search(21);
   printf("Element found: %d\n", item->data);
}

2.数组方式

#include 
#include 

#define SIZE 10
#define EMPTY -1

struct DataItem {
   int data;   
   int key;
} hashArray[SIZE];

// Initialize the hash table
void init()
{
   int i;
   for (i = 0; i < SIZE; i++) 
   {
      hashArray[i].key = EMPTY;
   }
}

int hashCode(int key) {
   return key % SIZE;
}

void insert(int key,int data) {
   int i=0;
   struct DataItem item;
   item.data = data;  
   item.key = key;

   int hashIndex = hashCode(key);
   while (hashArray[hashIndex].key != EMPTY) {
      // Go to next cell
      ++hashIndex;
      // Wrap around the table
      hashIndex %= SIZE;
      
      if(i++ > SIZE)
      {
          printf("data inset full-- key:%d,data:%d error\r\n",key,data);
          break;
      }
   }
   hashArray[hashIndex] = item;
}

struct DataItem *search(int key) {
   int hashIndex = hashCode(key);  
   while (hashArray[hashIndex].key != key) {
      // Go to next cell
      ++hashIndex;
      // Wrap around the table
      hashIndex %= SIZE;
   }
   return &hashArray[hashIndex];
}

void display() {
   int i;
   
   for(i = 0; i<SIZE; i++) 
   {
       if (hashArray[i].key != EMPTY)
       {
         printf(" (%d,%d)",hashArray[i].key,hashArray[i].data);
       } 
       else {
         printf(" ~~ ");
       }
   }
   printf("\n");
}


int main() {
    
   init();
   insert(1, 20);
   insert(2, 70);
   insert(42, 80);
   insert(4, 25);
   insert(12, 44);
   insert(14, 32);
   insert(17, 11);
   insert(13, 78);
   insert(37, 97);
   insert(11, 1);
   insert(21, 3);

   display();

   struct DataItem *item;
   item = search(37);

   if(item != NULL) {
      printf("Element found: %d\n", item->data);
   } else {
      printf("Element not found\n");
   }
   
   item = search(2);
      printf("Element found: %d\n", item->data);
   item = search(12);
      printf("Element found: %d\n", item->data);
   
   
   return 0;
}