import java.util.Arrays; import edu.princeton.cs.algs4.In;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut; /**
* The {@code BinarySearch} class provides a static method for binary
* searching for an integer in a sorted array of integers.
* <p>
* The <em>indexOf</em> operations takes logarithmic time in the worst case.
* <p>
* For additional documentation, see <a href="https://algs4.cs.princeton.edu/11model">Section 1.1</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class BinarySearch { /**
* This class should not be instantiated.
*/
private BinarySearch() { } /**
* Returns the index of the specified key in the specified array.
*
* @param a the array of integers, must be sorted in ascending order
* @param key the search key
* @return index of key in array {@code a} if present; {@code -1} otherwise
*/
public static int indexOf(int[] a, int key) {
int lo = 0;
int hi = a.length - 1;
while (lo <= hi) {
// Key is in a[lo..hi] or not present.
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;
} /**
* Returns the index of the specified key in the specified array.
* This function is poorly named because it does not give the <em>rank</em>
* if the array has duplicate keys or if the key is not in the array.
*
* @param key the search key
* @param a the array of integers, must be sorted in ascending order
* @return index of key in array {@code a} if present; {@code -1} otherwise
* @deprecated Replaced by {@link #indexOf(int[], int)}.
*/
@Deprecated
public static int rank(int key, int[] a) {
return indexOf(a, key);
} /**
* Reads in a sequence of integers from the whitelist file, specified as
* a command-line argument; reads in integers from standard input;
* prints to standard output those integers that do <em>not</em> appear in the file.
*
* @param args the command-line arguments
*/
public static void main(String[] args) { // read the integers from a file
In in = new In(args[0]);
int[] whitelist = in.readAllInts(); // sort the array
Arrays.sort(whitelist); // read integer key from standard input; print if not in whitelist
while (!StdIn.isEmpty()) {
int key = StdIn.readInt();
if (BinarySearch.indexOf(whitelist, key) == -1)
StdOut.println(key);
}
}
}
这是代码，官网上最新的代码。课本上的有一点错误。
0.将algs4.jar添加到环境变量
我是新建了一个文件夹algs4,在里面存放了algls4.jar 和 algs4-date两个文件
将algs4.jar包所在的地址添加到classpath后面。
1.引入algs4.jar
右键点击工程文件，我这里是BinarySearch,然后选中properties.
再选中java build path, libraries。
右击classpath，点击add extern jars
打开algs4.jar所在的地址
选中algs4.jar即可。这样就导入了algs4.jar这个包.
2.使用eclipse的run as 进行重定向
注意：这里的input file地址：是要输入的文件的地址。
点击隐藏的选项卡，选中argument
在program argument中填入largeW.txt(白名单)
然后运行即可.
特别注意：
此处我的largeW.txt和largeT.txt在同一个文件夹里。也就是说代码工程文件里放了largeT.txt和largeW.txt文件