算法学习 - Hash Table操作，分离链接法解决哈希冲突

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分离链接法

hash table是映射机制的，最大的优点就是它的操作是O(1)级别的。但是会出现哈希冲突，这就需要几种办法来解决。这里先说一种：分离链接法。

就是当插入的位置已经存在一个值之后，那么在这个值之后插入，就可以了，也叫拉链法。（但是其实会降低查找速度，变成O(n)级别）

下面是代码：

////  main.cpp//  HashTable_SeparateChaining////  Created by Alps on 14-8-5.//  Copyright (c) 2014年 chen. All rights reserved.//#include <iostream>#include <math.h>#include "HashTable.h"#define MinTableSize 1using namespace std;bool Prime(int size){    for (int i = 2; i < sqrt(size); i++) {        if (size%i == 0) {            return false;        }    }    return true;}int NextPrime(int Tablesize){    if (Tablesize <= 2) {        return 2;    }else{        while (!Prime(Tablesize)) {            Tablesize++;        }        return Tablesize;    }    return Tablesize;}HashTable InitializeTable(int Tablesize){    HashTable H;    int i;        if (Tablesize < MinTableSize) {//        Error("table size is too small!");        exit(0);    }    H = (HashTable)malloc(sizeof(struct HashTb));    if (H == NULL) {        //Error("out of space");        exit(0);    }    H->Tablesize = NextPrime(Tablesize);    H->TheList = (List*)malloc(sizeof(List) * H->Tablesize);    for (i = 0; i < H->Tablesize; i++) {        H->TheList[i] = (List)malloc(sizeof(struct ListNode));        H->TheList[i]->Next = NULL;    }        return H;}int Hash(int key, int Tablesize){    return key%Tablesize;}Position Find(ElementType key, HashTable H){    int i = Hash(key, H->Tablesize);    List L = H->TheList[i]->Next;    while (L != NULL && L->element != key) {        L = L->Next;    }    return L;}void Insert(ElementType key, HashTable H){    if (Find(key, H) == NULL) {        int i = Hash(key, H->Tablesize);        List L = (List)malloc(sizeof(struct ListNode));        L->element = key;        Position P = H->TheList[i];        L->Next = P->Next;        P->Next = L;    }}int main(int argc, const char * argv[]){    HashTable H = InitializeTable(10);    printf("%d\n",H->Tablesize);    Insert(5, H);    Insert(3, H);    Position P = Find(5, H);    printf("%d\n",P->element);    return 0;}

下面是头文件：

////  HashTable.h//  HashTable_SeparateChaining////  Created by Alps on 14-8-5.//  Copyright (c) 2014年 chen. All rights reserved.//#ifndef HashTable_SeparateChaining_HashTable_h#define HashTable_SeparateChaining_HashTable_h#define ElementType intstruct ListNode;typedef struct ListNode *Position;struct HashTb;typedef HashTb *HashTable;HashTable InitializeTable(int Tablesize);void Destory(HashTable H);Position Find(ElementType key, HashTable H);void Insert(ElementType key, HashTable H);#endifstruct ListNode{    ElementType element;    Position Next;};typedef Position List;struct HashTb{    int Tablesize;    List * TheList;};

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