哈希的基本理解---按照某种函数存储地址
冲突问题：
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#define SIZE 20
struct DataItem { //键值
int data;
int key;
};
struct DataItem* hashArray[SIZE];
struct DataItem* dummyItem;
struct DataItem* item;
int hashCode(int key) {
return key % SIZE;
}
struct DataItem *search(int key){
//get the hash
int hashIndex = hashCode(key); //key%SIZE
//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;
}
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;
}
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;
}
// 显示所示数据项
void display(){
int i = 0;
for(i = 0; i<SIZE; i++) {
if(hashArray[i] != NULL)
printf(" (%d,%d)",hashArray[i]->key,hashArray[i]->data);
else
printf(" ~~ ");
}
printf("\n");
}
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);
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");
}
}