哈希表和碰撞算法

线性探测法

哈希表结构体

#include<iostream>
#include<string.h>
using namespace std;

#define MAX 100
struct HashTable{
	int count; //元素个数
	int p;
	int data[MAX]={0}; //数据域 
};

计算哈希算法，这里采用最常用的求余数法

int hash(int value,int p){
	return value%p;
}

插入元素，线性探测法

就是如果发生碰撞，就一直往前寻找空位子，所以P这个参数会影响碰撞的次数

int Insert(HashTable* table,int value)  //线性探测
{
	
	int address = hash(value,table->p);
	if(table->data[address]==0){
		table->data[address]=value;
	}else{
		if(table->count<MAX){
			
			while(table->data[address]!=0){
				address = (address+1)%MAX;
			}
			table->data[address] = value;
		}else{
			cout<<"满了"<<endl; 
		}
	}	
}

寻找元素的索引位置

int find(HashTable* table,int value) //查找值的位置 不存在返回-1
{
	int index = (value%table->p);
	int count=1;
	while(table->data[index]!=value && count<=(MAX+1)){
		count++;
		index = (index+1)%MAX;
	} 
	if(count>MAX){
		cout<<"找不到"<<endl;
		return -1;
	}else{
		return index;
	}
} 

void Delete(HashTable* table,int value){
	int index = find(table,value);
	if(index!=-1){
		table->data[index] = 0;
	}
}

删除元素

void Delete(HashTable* table,int value){
	int index = find(table,value);
	if(index!=-1){
		table->data[index] = 0;
	}
}

可执行的完整代码

#include<iostream>
#include<string.h>
using namespace std;

#define MAX 100
struct HashTable{
	int count; //元素个数
	int p;
	int data[MAX]={0}; //数据域 
};


int hash(int value,int p){
	return value%p;
}

int Insert(HashTable* table,int value)  //线性探测
{
	
	int address = hash(value,table->p);
	if(table->data[address]==0){
		table->data[address]=value;
	}else{
		if(table->count<MAX){
			
			while(table->data[address]!=0){
				address = (address+1)%MAX;
			}
			table->data[address] = value;
		}else{
			cout<<"满了"<<endl; 
		}
	}	
}

int find(HashTable* table,int value) //查找值的位置 不存在返回-1
{
	int index = (value%table->p);
	int count=1;
	while(table->data[index]!=value && count<=(MAX+1)){
		count++;
		index = (index+1)%MAX;
	} 
	if(count>MAX){
		cout<<"找不到"<<endl;
		return -1;
	}else{
		return index;
	}
} 

void Delete(HashTable* table,int value){
	int index = find(table,value);
	if(index!=-1){
		table->data[index] = 0;
	}
}
 


int main(){
	
	HashTable* table = new HashTable;
	table->p = 91;
	table->count=0;
	memset(table->data,0,sizeof(int)*MAX);
	Insert(table,986);
	Insert(table,1986);
	Insert(table,286);
	Insert(table,96);
	cout<<find(table,986)<<endl;
	cout<<find(table,1986)<<endl;
	cout<<find(table,96)<<endl;
	Delete(table,1986);
	cout<<find(table,1986)<<endl; 
	return 0;
} 

---

拉链法

结构体

#include<iostream>
#include<string.h>
using namespace std;
#define MAX 10
#define P 7
struct Node{
	int value;
	Node* next;
};

struct HashTable{
	int count=0;
	Node data[MAX]; 
};

插入元素，如果发生碰撞，就在当前节点的链表上插入

void Insert(HashTable* table,int value){
	int index = (value%P);
	if(table->data[index].value!=0){
		
		Node** node = &(table->data[index].next);
		while((*node)!=NULL)
			*node = (*node)->next;
		*node = new Node;
		(*node)->value = value;
		(*node)->next = NULL;
		
	}else{
		
		table->data[index].value = value;
	}
}

寻找元素

Node* find(HashTable* table,int val){
	int index = (val%P);
	if(table->data[index].value==val){
		return &table->data[index];
	}else{
		Node* node = table->data[index].next;
		while( node!=NULL&&node->value!=val){
			node = node->next;
		}
		return node;
	}
} 

删除元素

如果元素在链表上，那和删除链表节点一样，特殊情况需要考虑的就是头结点

如果是在哈希表上，则如果有链表，则将链表提升，没有的话直接清零

可执行代码

#include<iostream>
#include<string.h>
using namespace std;
#define MAX 10
#define P 7
struct Node{
	int value;
	Node* next;
};

struct HashTable{
	int count=0;
	Node data[MAX]; 
};


void Insert(HashTable* table,int value){
	int index = (value%P);
	if(table->data[index].value!=0){
		
		Node** node = &(table->data[index].next);
		while((*node)!=NULL)
			*node = (*node)->next;
		*node = new Node;
		(*node)->value = value;
		(*node)->next = NULL;
		
	}else{
		
		table->data[index].value = value;
	}
}

Node* find(HashTable* table,int val){
	int index = (val%P);
	if(table->data[index].value==val){
		return &table->data[index];
	}else{
		Node* node = table->data[index].next;
		while( node!=NULL&&node->value!=val){
			node = node->next;
		}
		return node;
	}
} 




int main(){
	HashTable* table = new HashTable;
	for(int i=0;i<MAX;i++){
		table->data[i].value=0;
		table->data[i].next=NULL;
	}
	Insert(table,1);
	Insert(table,8);
	Insert(table,9);
	Insert(table,6);
	Insert(table,2);
//	
	cout<<find(table,1)->next->value;
	
	
	return 0;
}