算法（Algorithms）第4版 练习 1.3.21

方法实现：

　　//1.3.21
    /**
     * find if some node in the list has key as its item field
     *
     * @param list the linked list of T
     * @param key the T key
     *
     * @return {@code true} some node exists.
     *          {@code false} no node exist
     */
    public static <T> boolean find(LinkedList<T> list, T key) {

        for(T s : list) {
            if(s.equals(key))
                return true;
        }

        return false;
    }

测试用例：

package com.qiusongde.linkedlist;

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class Exercise1321 {

    public static void main(String[] args) {

        LinkedList<String> list = new LinkedList<String>();

        while(!StdIn.isEmpty()) {
            String s = StdIn.readString();
            list.insertAtBeginning(s);
            StdOut.println("insertAtBeginning success: " + s);
            StdOut.println(list);
        }

        String key = "qiu";
        StdOut.println("find " + key + " :" + LinkedList.find(list, key));

        key = "not";
        StdOut.println("find " + key + " :" + LinkedList.find(list, key));

    }

}

输入数据：

to
be
or
not
to

输出结果：

insertAtBeginning success: to
to
insertAtBeginning success: be
be to
insertAtBeginning success: or
or be to
insertAtBeginning success: not
not or be to
insertAtBeginning success: to
to not or be to
find qiu :false
find not :true