2_3 递归与分治策略（二分搜索技术）

public class a_2_3<T extends Comparable> {
    public  static<T extends Comparable> int binarySearch(T []a,T x){ //二分查找
        int left=0,right=a.length-1,middle;
        while(left<=right){ //注意条件是<=，因为在上一次变化后因为left==right==middle这个middle值尚未探测。
            middle=(left+right)/2;
            if(a[middle].compareTo(x)==0)return middle;
            else if(a[middle].compareTo(x)<0) left=middle+1;
            else right=middle-1;
        }
        return -1;
    }

    public  static<T extends Comparable> int find(T []a,T x){ //顺序查找
        int i=0;
        while(i<a.length){
            if(a[i++].compareTo(x)==0)return i-1;
        }
        return -1;
    }
    public static void main(String []args){
        int MAX=10;
        Integer a[]=new Integer[MAX];
        for(int i=0;i<MAX;i++)a[i]=i;
        System.out.println(binarySearch(a,5));
    }
}