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;
}