halfsearch.java

1. 用二叉链表保存二叉树 2. 以基于二叉树的先序序列创建立二叉树 3. 按前序、中序、后序遍历二叉树（三选一）

import java.util.Scanner;

class HalfSearch 
{
	public final int NUM=5;
	private int[] r;
	private int key;
	
	public HalfSearch()
	{
		r=new int[NUM];
	}
	
	public void input()
	{
		Scanner scan=new Scanner(System.in);
		System.out.println("请输入"+NUM+"个整数(从小到大）：");
		for(int i=0;i<NUM;i++){
			r[i]=scan.nextInt();
		}
		System.out.println("请输入待查找的数据：");
		key=scan.nextInt();
	}
	
	public int search()  //二分查找 Log2 n
	{
		int low=1;
		int high=r.length-1;
		int mid=0;
		int i=0;
		while(low<=high){
			i++;
			mid=(low+high)/2;
			if(key==r[mid]){
				System.out.println("已找到待查找的数据！");
				break;
			}
			else if(key<r[mid])
			high=mid-1;
			else 
			low=mid+1;				
		}
		if(low>high)
		System.out.println("待查找数据不存在！");
		return i;
	}
}