散列表

哦算法4上符號表的實現少了一個判斷first是否爲null的情況= =

拉鍊法散列表實現如下:

/**
 * Created by eminem on 16-11-22.
 */


//拉鍊法散列表


public class sanLieBiao {
    private int N;

    //鏈表數量
    private int M;
    private SequentialSearchST<String, Integer>[] st;

    public sanLieBiao() {
        this(997);
    }

    public sanLieBiao(int M) {
        this.M = M;
        st = (SequentialSearchST<String, Integer>[]) new SequentialSearchST[M];
        for (int i = 0; i < M; i++) {
            st[i] = new SequentialSearchST();
        }
    }


    private int hash(String key) {
        return (key.hashCode() & 0x7fffffff) % M;
    }

    public Integer get(String key) {
        return st[hash(key)].get(key);
    }

    public void put(String key, Integer val) {
        st[hash(key)].put(key, val);
    }

    public Integer delete(String key){
        return st[hash(key)].delete(key);
    }






    //此處還應該有一個迭代器
//    public Iterable<String> keys(){
//
//    }
}


class SequentialSearchST<String, Integer> {
    private Node first;

    private class Node {
        String Key;
        Integer val;
        Node next;

        public Node(String key, Integer val, Node next) {
            this.Key = key;
            this.val = val;
            this.next = next;
        }
    }




    public Integer get(String key) {

        for (Node x = first; x != null; x = x.next) {
            if (key.equals(x.Key)) {
                return x.val;
            }
        }
        System.out.println("get:Can't find the key"+"="+"\""+key+"\"");
        return null;
    }

    public void put(String key, Integer val) {
        if (first == null) {
            first = new Node(key, val, first);
            return;
        } else {
            for (Node x = first; x != null; x = x.next) {
                if (key.equals(x.Key)) {
                    x.val = val;
                    return;
                }
            }

            first = new Node(key, val, first);
        }
    }

    public Integer delete (String key) {
        //如果這條鏈表本身就是空的
        if(first==null){
            System.out.println("delete:Can't find the key"+"="+"\""+key+"\"");
            return null;
        }

        Node x = first;
        Node y = x;

        //如果該條鏈表不是空的那就讓這兩個指針一前一後走到合適的位置
        while (!key.equals(x.Key)) {
            y = x;
            x = x.next;
            if(x==null){
                System.out.println("delete:Can't find the key"+"="+"\""+key+"\"");
                return null;
            }
        }



        Integer fuck=x.val;

        //處理不同位置的x
        if(x==first){
            first=null;
        }else{
            y.next=x.next;
        }

        return fuck;

    }
}

testClass:

public class Fucktest{
    public static void main(String[] args) {
        sanLieBiao sanlie=new sanLieBiao();

        int num=1;
        char i = 'a';
        for (; i <'z'+1; i++,num++) {
            sanlie.put(String.valueOf(i),num);

        }

        i='a';
        for(int tmp=1;tmp<27;tmp++){

            System.out.println(sanlie.get(String.valueOf(i++)));
        }



    }
}

md這個刪除函數好難調啊。。