题目要求：用折半查找法判断一个从键盘上输入的数是否在某个数组中。

代码：mport java.util.*;
public class SortFind {
    public static void main(String args[]) {
        int n=0, low, high, middle;
        System.out.println("从键盘输入一个整数，程序将判断该数是否在一个数组中");
        int a[] = {12,34,9,-23,45,6,45,90,123,19,34};
        Arrays.sort(a);   
        Scanner reader = new Scanner(System.in);
            while(reader.hasNextInt()){
        n = reader.nextInt();
                low = 0;
        high= a.length;
        middle = (low + high)/2;
        while (low<=high) {
            middle = (low + high)/2;
            if (n == a[middle] ) {
                System.out.println(n + "是数组中的元素");
                break;
            } else if (n < a[middle]) {
                high=a[middle]-1;
            } else {
                low=a[middle]+1;
            }
        }
        if (low==high) {
            System.out.println(n + "不在数组中");
        }
 }
    System.out.println("\n可继续输入整数，或输入非整数结束程序");
      
    System.out.println("你输入的数据不是整数");
    }
}

  while (low<=high) {
            middle = (low + high)/2;
            if (n == a[middle] ) {
                System.out.println(n + "是数组中的元素");
                break;
            } else if (n < a[middle]) {
                high=a[middle]-1;    //high = middle - 1;
            } else {
                low=a[middle]+1;     //high = middle + 1;
            }
        }

这里是改变下标的。

顶LS

刚学完C++，java还是起步阶段。呵呵！谢谢~