BinarySearch(二分查找）

//二分查找package Algorithms;import java.util.Arrays;import edu.princeton.cs.algs4.In;import edu.princeton.cs.algs4.StdIn;import edu.princeton.cs.algs4.StdOut;public class P28_BinarySearch {public static int rank(int key, int[]a){//数据必须是有序的int lo = 0;int hi = a.length - 1;while (lo <= hi){//被查找的键值要么不存在，要么必然存在于a[lo..hi]之中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) {// TODO Auto-generated method stubIn in = new In(args[0]);int[] whitelist = in.readAllInts();Arrays.sort(whitelist);while (!StdIn.isEmpty()){//读取键值，如果不存在于白名单中则将其打印int key = StdIn.readInt();if (rank(key, whitelist) < 0){StdOut.println(key);}}}}