public class A{
public static void main(String[] args){
int[] nums={-1,1,3,19,55,66}; //降序 66 55 19 3 1 -1
int num=66;
int index=A.getIndex(nums,num);
System.out.println(index);
}
//算法复杂度极高 遍历 n/2的数据取查找 折半查找 log2N
public static int getIndex(int[] arr,int num){
int min=0;
int max=arr.length-1;
while(min <=max){
int mid=(min+max)/2;
if(num == arr[mid]){
return mid;
}else if(num < arr[mid]){
max=mid-1;
}else{
min=mid+1;
}
}
return -1;
}
}