Algs4-1.1.38二分查找与暴力查找

1.1.38二分查找与暴力查找。根据1.1.10.4节给出的暴力查找法编写一个程序BruteForceSearch,在你的计算机上比较它和BinarySearch处理largeW.txt和largeT.txt所需的时间。
解：
暴力查找约用时：2371秒
二分查找约用时: 17秒

//暴力查找代码
import java.util.Date;
public class BruteForceSearch
{
    public static int rank(int key,int[] a)
    {
       for (int i=0;i<a.length;i++)
           if (a[i]==key) return i;
       return -1;
    }//end rank 
 
    public static void main(String[] args)
    {
        int[] whitelist=In.readInts(args[0]);
        int postion;
        Date timeStart=new Date();
        while (!StdIn.isEmpty())
        {
            int key=StdIn.readInt();
            postion=rank(key,whitelist);
        }  
        Date timeEnd=new Date();
        StdOut.printf("BruteForceSearch used time:");
        StdOut.println(timeEnd.getTime()-timeStart.getTime());
    }
}

//二分查找代码
import java.util.Date;
import java.util.Arrays;
public class BinarySearch
{
    public static int rank(int key,int[]a)
    {
        int lo=0;
        int hi=a.length-1;
        while (lo<=hi)
        {
            int mid=lo+(hi-lo)/2;
            if (key<a[mid]) hi=mid-1;
            else if(key>a[mid]) lo=mid+1;
            else return mid;
          }
        return -1;
     }

public static void main(String[] args)
    {
        int[] whitelist=In.readInts(args[0]);
        int postion;
        Date timeStart=new Date();
        Arrays.sort(whitelist);
        while (!StdIn.isEmpty())
        {
            int key=StdIn.readInt();
            postion= rank(key,whitelist);
        }
        Date timeEnd=new Date();
        StdOut.printf("BinarySearch used time:");
        StdOut.println(timeEnd.getTime()-timeStart.getTime());
    }
}

原文地址：https://www.cnblogs.com/longjin2018/p/9848760.html