java中的二分查找

package test;


public class project1 {
		public static void main(String []args) {
			int []list= {1,3,4,5,6,7,9,12,13,15,18,19};
			int key=12;
            int result=binarySearch(list,key);
            if(result<0) {
            	System.out.println("not found the number:"+key);
            }else {
            	System.out.println("the index of "+key+" is "+result);
            }
		}
		public static int binarySearch(int []list,int key) {
			int low=0;
			int hight=list.length-1;
			int mid;
			while(low<=hight) {
				mid=(low+hight)/2;
				if(list[mid]<key) 
					low=mid+1;
				else if(list[mid]==key)
					return mid;
				else hight=mid-1;
		    }
			return -low-1;
		}
}

递归二分查找：

package test;


public class project1 {
		public static void main(String []args) {
			int []list= {1,3,4,5,6,7,9,12,13,15,18,19};
			int key=12;
			int low=0;
			int hight=list.length-1;
            int result=binarySearch(list,key,low,hight);
            if(result<0) {
            	System.out.println("not found the number:"+key);
            }else {
            	System.out.println("the index of "+key+" is "+result);
            }
		}
		public static int binarySearch(int []list,int key,int low,int hight) {
			int mid=(low+hight)/2;
				if(list[mid]<key) 
					return binarySearch(list,key,mid+1,hight);
				else if(list[mid]==key)
					return mid;
				else return binarySearch(list,key,low,mid-1);
		}
}