[清华集训 2014] Sum

ID: 4137

远端评测题

1000ms

250MiB

难度: 9

上传者:

标签>

2014

CTT（清华集训/北大集训）

Problem Description

Given positive integers $n$ and $r$ , compute:

\sum_{d=1}^{n}(-1)^{\lfloor d\sqrt{r} \rfloor}

The first line contains an integer $t$ , indicating that there are $t$ testdata cases.

The next $t$ lines each contain two positive integers $n$ and $r$ .

Output $t$ lines, each containing one integer representing the answer.

3
1
-1

Test Point ID	$t$	$n$	$r$
$1 \sim 3$	$\leqslant 10$	$\leqslant 10^5$	$\leqslant 100$
$4 \sim 6$	$\leqslant 100$	$\leqslant 10^7$	$\leqslant 1000$
$7 \sim 10$	$\leqslant 10^4$	$\leqslant 10^9$	$\leqslant 10^4$

Translated by ChatGPT 5