学步园

//核心本身已经是有序数组

public class BinarySearch {
 public static int binarySearch(int[] arrs, int val){
  return binarySearch( 0,arrs.length-1,val,arrs);
 }
 public static int  binarySearch(int low, int heigh, int val ,int[] arrs){
  int mid = (low + heigh)/2;
  if(low <= heigh){
   if(arrs[mid] == val)
    return mid;

//找左边
   if(arrs[mid] > val)
    return binarySearch(low,mid-1,val,arrs);

//找右边

   if(arrs[mid] < val)
    return binarySearch(mid+1,heigh,val,arrs);
  }
  return -1;
 }
 public static void main(String[] args) {
   int[] a = new int[]{1,2,3,4,5,6,7};
   System.out.println(binarySearch(a,7));
 }

}