二分模板

//左边界
public static int bSearch1(int l, int r){
   while (l < r){
       int mid = l + r >> 1;
       if (check(mid)) r = mid;
       else l= mid + 1;
   }
   return l;
}

//右边界
public static int bSearch2(int l, int r){
   while (l < r){
       int mid = l + r  + 1 >> 1;
       if (check(mid)) l = mid;
       else r = mid - 1;
   }
   return l;
}