Chapter11:哈希表的建立和使用

最新推荐文章于 2025-05-12 14:20:34 发布

lily0806

最新推荐文章于 2025-05-12 14:20:34 发布

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分类专栏：数据结构

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本文详细介绍了哈希表的建立、使用实例，包括插入、删除、查找等操作，通过控制台交互方式实现，适用于数据结构与算法学习。

package Chapter11;

import java.util.Scanner;

public class Hash {

/**
* @哈希表的建立和使用实例
*/
public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);

  DataItem aDataItem;
  int aKey,size,n,keysPerCell;
  sop("Enter size of hash table: ");
  size = Integer.parseInt(sc.nextLine()); //hashTable的大小

  sop("Enter initial number of items: ");
  n = Integer.parseInt(sc.nextLine());     //hashTable开始有的值

  keysPerCell = 10;

  HashTable theHashTable = new HashTable(size);

  for(int j = 0;j<n;j++){
   aKey = (int) (Math.random()*keysPerCell*size);
   aDataItem = new DataItem(aKey);
   theHashTable.insert(aDataItem);
  }

  while(true){
   sop("Enter first letter of: ");
   sop("show , insert , delete , find : ");
   char choise = sc.nextLine().charAt(0);
   switch(choise){
    case 's':
     theHashTable.displayTable();
     break;
    case 'i':
     sop("Enter key value to insert: ");
     aKey = Integer.parseInt(sc.nextLine());
     aDataItem = new DataItem(aKey);
     theHashTable.insert(aDataItem);
     break;
    case 'd':
     sop("Enter key value to delete: ");
     aKey = Integer.parseInt(sc.nextLine());
     theHashTable.delete(aKey);
     break;
    case 'f':
     sop("Enter key value to find: ");
     aKey = Integer.parseInt(sc.nextLine());
     aDataItem = theHashTable.find(aKey);
     if(aDataItem==null)
      sop("not find: "+aKey);
     else
      sop("find: "+aKey);
     break;
    default:
     sop("invalid entry\n");
   }
  }

}
public static void sop(Object o){
  System.out.print(o);
}

}
class DataItem{
private int iData;
public DataItem(int id){
  iData = id;
}
public int getKey(){
  return iData;
}
}
class HashTable{
private DataItem[] hashArray;
private int arraySize;
private DataItem nonItem;

public HashTable(int size){
  arraySize = size;
  hashArray = new DataItem[arraySize];
  nonItem = new DataItem(-1);
}

public void displayTable(){
  System.out.println("display table: ");
  for(int i=0;i<arraySize;i++){
   if(hashArray[i]!=null)
    System.out.print(hashArray[i].getKey()+" ");
   else
    System.out.print("**");
  }
  System.out.println("-----------------------");
}

public int hashFunc(int key){
  return key % arraySize;
}
public void insert(DataItem item){
  int key = item.getKey();
  int hashVal = hashFunc(key);

  while(hashArray[hashVal]!=null && hashArray[hashVal].getKey()!=-1){
   hashVal++;
   hashVal = hashVal % arraySize;
  }
  hashArray[hashVal] = item;
}

public DataItem delete(int key){
  int hashVal = hashFunc(key);
  while(hashArray[hashVal]!=null){
   if(hashArray[hashVal].getKey()==key){
    DataItem temp = hashArray[hashVal];
    hashArray[hashVal] = null;
    return temp;
   }
   hashVal++;
   hashVal = hashVal % arraySize;
  }
  return null;
}

public DataItem find(int key){
  int hashVal = hashFunc(key);
  while(hashArray[hashVal]!=null){
   if(hashArray[hashVal].getKey() == key){
    DataItem temp = hashArray[hashVal];
    return temp;
   }
   hashVal++;
   hashVal = hashVal % arraySize;
  }
  return null;
}
}