001-SE-0004-二分法查找

* 二分查找的数组只能是从大到小排列的，或从小到大排列的
* 当max<min时就返回-1

@Test
public void testName7() throws Exception {
	//int[] arr={34,19,11,109,3,56};
	int[] arr={13,24,36,41,66,78,109};
	int index = halfSerarch(arr,109);
	System.out.println(index);
}
	
public int halfSerarch(int[] arr,int key){
	int max,min,mid;
	min=0;
	max=arr.length-1;
	mid=(max+min)/2;
	while(arr[mid]!=key){
		if(key>arr[mid]){
			min=mid+1;
		}else if(key<arr[mid]){
			max=mid-1;
		}
		if(max<min){
			return -1;
		}
		mid=(max+min)/2;
	}
	return mid;
}