PracticeDev/study_cpp/hashmap_test/hash_map_test.cpp

#include<iostream>
#include <stdio.h>
#include <memory.h>
#include <string.h>
#include <stdlib.h>
using namespace std;
 
#define HARSH_TABLE_MAX_SIZE   (1000) // 哈希数组的最大元素个数
 
typedef struct HarshNode_struct HarshNode;
 
// 定义一个哈希表的节点
struct HarshNode_struct
{
	char * sKey;   // [sKey,nvalue]是一对键值对
	int nValue;
	HarshNode *pNext;
};
 
HarshNode * harshTable[HARSH_TABLE_MAX_SIZE]; // 哈希表数组
unsigned int g_harsh_table_size = 0x0;
 
 
 
//初始化哈希表
void harsh_table_init(void)
{
	int i = 0x0;
	memset(harshTable,0,sizeof(HarshNode *)*HARSH_TABLE_MAX_SIZE);
	g_harsh_table_size = 0x0;
}
 
 
// string harsh function
unsigned int harsh_table_harsh_string(const char * sKey)
{
	const unsigned  char* p =  (const unsigned  char*) sKey;
	unsigned int value = *p;
 
	if(value)
	{
		for( p += 1; *p != '\0'; p++)
		{
			value = (value << 5) - value + *p;  
		}
	}
 
	return value;
 
}


//根据键值对向哈希表中添加节点，如果skey已经存在则直接更新键值nValue
//添加成功返回0，添加失败返回-1
int harsh_table_insert_node(const char * sKey, int nValue)
{
	HarshNode * pHarshNodeHead   = NULL;
	HarshNode * pNewNode = NULL; 
	unsigned int pos = 0x0;
 
	if((g_harsh_table_size >= HARSH_TABLE_MAX_SIZE )||(NULL  == sKey))
		return -1;
	
	 pos =  harsh_table_harsh_string(sKey) % HARSH_TABLE_MAX_SIZE; //用这种方法计算sKey在哈希数组中对应的位置

	 printf("harsh_table_insert_node : pos = %d\n",pos);
 
	pHarshNodeHead = harshTable[pos];
 
	if(NULL == pHarshNodeHead)
	   printf("harsh_table_insert_node:NULL == pHarshNodeHead\n");	
 
	while(NULL != pHarshNodeHead )  // 如果这个位置对应的不是这一串中最后一个节点的话，那就要向后移动了
    {
		if(strcmp(pHarshNodeHead->sKey,sKey) == 0) //如果这个键值对已经存在，只更新键值即可
		{
			pHarshNodeHead ->nValue = nValue;
			return 0;
		}
		pHarshNodeHead = pHarshNodeHead->pNext;  //向后移动,肯定会有NULL的时候
	}
 
	pNewNode = (HarshNode *)malloc(sizeof(HarshNode)); //申请一块HarshNode 大小的内存
	if(NULL == pNewNode)
    {
		return -1;
	}
	memset(pNewNode,0,sizeof(HarshNode));
 
	pNewNode ->sKey = (char *)malloc(strlen(sKey) + 1); //申请一块sKey大小的内存
	if(NULL == pNewNode ->sKey )
	{
		return -1;
	}
	memset(pNewNode ->sKey,0,strlen(sKey) + 1);
 
	strcpy(pNewNode ->sKey,sKey); //将sKey的内容赋给 pNewNode -> sKey
	pNewNode ->nValue = nValue; //键值也复制过来
 
	pNewNode ->pNext = NULL; //由于是新节点，也是尾节点，所以pNext指向NULL
 
	pHarshNodeHead  = pNewNode;
	harshTable[pos] = pHarshNodeHead; //最后一定要让数组中的这个位置指向这个头指针
 
	g_harsh_table_size ++;
 
	return 0;
 
 
}
 
 
//打印数组中对应的某个位置的那一串哈希值
void print_harsh_node(int pos)
{
	HarshNode * pHarshNodeHead   = NULL;
 
	if(pos >= HARSH_TABLE_MAX_SIZE)
		return;
 
	pHarshNodeHead = harshTable[pos];
 
	if(NULL == pHarshNodeHead)
	   printf("NULL == pHarshNodeHead\n");	
	while(NULL != pHarshNodeHead)
    {
		printf("come here \n");
		printf("Position:%d, sKey:%s, nValue:%d \n",pos,pHarshNodeHead->sKey,pHarshNodeHead->nValue);
		pHarshNodeHead = pHarshNodeHead->pNext;
 
	}
 
 
}
 
// 根据键值sKey来查找对应的哈希节点
HarshNode * harsh_table_lookup(const char *sKey)
{
	unsigned int pos = 0x0;
	HarshNode * pHarshHead = NULL;
 
	if(NULL == sKey)
	{
		return NULL;
	}
 
	pos = harsh_table_harsh_string(sKey) % HARSH_TABLE_MAX_SIZE; //计算出在哈希数组中的位置
 
	pHarshHead = harshTable[pos];
	
	while(NULL != pHarshHead)
	{
		if(strcmp(sKey,pHarshHead->sKey) == 0)//找到了
			return pHarshHead;
 
		pHarshHead = pHarshHead->pNext; // 没有找到的话来到下一个节点
	}
 
	return NULL;
 
}
 
 
 
int main(void)
{
	char * pSkey = "abcd";
	int nValue = 1234;
	int ret = -1;
	int pos = 0xffffffff;
	HarshNode * pHarshNode = NULL;
 
	harsh_table_init();
	ret = harsh_table_insert_node(pSkey,nValue);
 
	printf("ret = %d\n",ret);
 
 
	if(!ret)
    {
		pos = harsh_table_harsh_string(pSkey) % HARSH_TABLE_MAX_SIZE;
		printf("main:  pos = %d\n",pos);
		print_harsh_node(pos);
	}
 
	pHarshNode = harsh_table_lookup(pSkey);
 
	if(NULL != pHarshNode)
	{
		printf("Got it: sKey:%s, nValue: %d\n",pHarshNode->sKey,pHarshNode->nValue);
	}

    return 0;
	
}