复习计划里的低级错误

luoguP2678 跳石头

　　二分的边界判断应该是

1     for (int mid = (l+r)>>1; l <= r; mid = (l+r)>>1)
2         if (check(mid)) ans = mid, l = mid+1;
3         else r = mid-1;

而不是

1     for (int mid = (l+r)>>1; l < r; mid = (l+r)>>1)
2         if (check(mid)) ans = mid, l = mid+1;
3         else r = mid;

 cf230A. Dragons

用sort时候写了cmp结果没调用