HashTable 解决碰撞（冲突）的方法 —— 分离链接法（separate chaining）

1. ListNode 及 HashTable 的类型声明

• 声明

  typedef int ElementType;
  typedef unsigned int Index;
  
  struct ListNode;
  typedef struct ListNode* Position;
  struct HashTbl;
  typedef struct HashTbl* HashTable;
  
  HashTable InitHashTable(int TableSize);
  void DestroyHashTable(HashTable H);
  Position Find(ElementType Element, HashTable H);
  void Insert(ElementType Element, HashTable H);;
  ElementType Retrieve(Position P);

• 定义

  struct ListNode{
      ElementType Element;
      Position Next;  
  };
  
  typedef Position List;
  
  struct HashTbl {
      int TableSize;
      List* TheLists; 
  };

2. HashTable 的构建

HashTable InitHashTable(int TableSize){
    HashTable H;
    if (TableSize < MinTableSize){
        Error(" ... ");
        return NULL;
    }

    H = (HashTable)malloc(sizeof(struct HashTbl));
    if (!H)
        FatalError("out of space !!!");
    H->TableSize = NextPrime(TableSize);
    H->TheLists = (List*)malloc(sizeof(struct ListNode)*H->TableSize);

    for (int i = 0; i < H->TableSize; ++i){
        H->TheLists[i] = (List)malloc(sizeof(struct ListNode));
        if (!H->TheLists[i])
            FatalError("");
        else
            H->TheLists[i]->Next = NULL;
    }
}

3. 插入新的结点

void Insert(ElementType Key, HashTable H){
    Position Pos, NewCell;
    List L;
    Pos = Find(key, H);
    if (!Pos){
        NewCell = (Position)malloc(sizeof(struct ListNode));
        if (!NewCell)
            FatalError("");
        L = H->TheLists[Hash(Key, H->TableSize)];
        NewCell->Next = L->Next;
                                    // 插入在首部
        NewCell->Element = Key;
        L->Next = NewCell->Next;
    }
}