20200202数据结构和算法之 哈希表

哈希表!是为了根据key值和哈希函数（一般是key值对tabsize取模），快速找到对应的数据而生，其数据结构组成如下：

#define DEFAULT_SIZE 128
typedef struct _listNode {
	struct _listNode* next;
	int key;
	void* data;
}listNode;

typedef listNode* list;
typedef listNode* element;

typedef struct _hashTable {
	int tableSize;
	list* theLists;
}hashTable;

根据数据结构组成，其由哈希表头、哈希桶、数据结点组成，其中数据结点包含有键值、next指针和void*型的数据。list是哈希桶指针，element是数据结点指针，其实他们是一回事，只是为了区分而已。需要说明的哈希桶的data为空，key也只是占位的作用，起作用的是next指针，指向真正的listNode。
key---->哈希函数---->索引值（哈希桶的下标）---->哈希桶对应的列表–>找到对应的node结点

#include<Windows.h>
#include<iostream>
#include<stdio.h>
#include <string>
#include <string.h>
using namespace std;
#define DEFAULT_SIZE 128
typedef struct _listNode {
	struct _listNode* next;
	int key;
	void* data;
}listNode;

typedef listNode* list;
typedef listNode* element;

typedef struct _hashTable {
	int tableSize;
	list* theLists;
}hashTable;

hashTable* initHash(int tableSize);
int hashFunction(int key, int tableSize);//哈希函数
element findElement(hashTable* hashTable, int key);
bool insertElement(hashTable* hashTable, int key,void* value);
bool deleteElement(hashTable* hastTable, int key);

int main() {
	const char *str[] = { "如花",(char*)"小芳",(char*)"苍井空",(char*)"夏老师" };
	char str1[] = { "如花" };

	int i = 0;
	

	hashTable* hashTab = initHash(30);
	for (int i = 0; i < 4; i++) {
		if (insertElement(hashTab, i,(char*) str[i])) {
			cout << "插入成功！" << endl;
		}
		else {
			cout << "插入失败！" << endl;
		}
	}
	
	if (!deleteElement(hashTab, 3))
		cout << "删除失败！" << endl;

	for (int i = 0; i < 4; i++) {
		element E = findElement(hashTab, i);
		if (E) {
			cout << "找到的元素为:" <<(char*)( E->data) << endl;
		}
		else
		    cout << "未找到key"<<i<<"对应的元素" << endl;
	}

	system("pause");
	return 0;
}
hashTable* initHash(int tableSize) {
	int i = 0;
	hashTable* hTable = NULL;
	if (tableSize <= 0) {
		tableSize = DEFAULT_SIZE;
	}
	hTable = (hashTable*)malloc(sizeof(hashTable));
	if (hTable == NULL) {
		cout << "hashTable malloc failure" << endl;
		return NULL;
	}
	hTable->tableSize = tableSize;

	//为哈希桶分配内存空间，其为一个指针数组
	hTable->theLists = (list*)malloc(tableSize * sizeof(list));
	if (hTable->theLists == NULL) {
		cout << "theLists malloc failure" << endl;
		free(hTable);
		return NULL;
	}

	//为哈希桶对应的指针数组初始化链表结点
	for (int i = 0; i < tableSize; i++) {
		hTable->theLists[i] = (listNode*)malloc(sizeof(listNode));
		if (hTable->theLists[i] == NULL) {
			cout << "theLists malloc failure" << endl;
			free(hTable->theLists);
			free(hTable);
			return NULL;
		}
		memset(hTable->theLists[i], 0, sizeof(listNode));
	}
	return hTable;
}
int hashFunction(int key, int tableSize) {
	/*根据 key 计算索引，定位 Hash 桶的位置*/
	return (key % tableSize);
}
element findElement(hashTable* hashTable, int key) {
	int i = 0;
	list L = NULL;
	element E = NULL;
	i = hashFunction(key, hashTable->tableSize);
	L = hashTable->theLists[i];
	E = L->next;
	while (E != NULL && E->key != key) {
		E = E->next;
	}
	return E;
}
bool insertElement(hashTable* hashTable, int key, void* value) {
	element E = NULL, tmp = NULL;
	list L = NULL;
	E = findElement(hashTable, key);
	if (E == NULL) {
		tmp = (listNode*)malloc(sizeof(listNode));
		if (tmp == NULL) {
			printf("listNode malloc failure!");
			return false;
		}
		tmp->data = value;
		tmp->key = key;
		tmp->next = NULL;

		L = hashTable->theLists[hashFunction(key,hashTable->tableSize)];
		tmp->next = L->next;
		L->next = tmp;
		return true;
	}
	else {
		cout << "element already exits" << endl;
		return false;
	}
		
}
bool deleteElement(hashTable* hashTable, int key) {
	element E = NULL;
	element pre = NULL;
	int index = hashFunction(key, hashTable->tableSize);
	pre = hashTable->theLists[index];
	E = hashTable->theLists[index]->next;
	while (E->key != key && E != NULL) {
		pre = E;
		E = E->next;
	}
	if (E) {
		pre->next = E->next;
		delete E;
		return true;
	}
	return 	false;
}