AtCoder Regular Contest 156
D
Xor Sum 5
AtCoder
⌀ 2568
原题
← CE →
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Problem Statement

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You are given a sequence of $N$ non-negative integers $A=(A_1,A_2,\dots,A_N)$ and a positive integer $K$.

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Find the bitwise $\mathrm{XOR}$ of $\displaystyle \sum_{i=1}^{K} A_{X_i}$ over all $N^K$ sequences of $K$ positive integer sequences $X=(X_1,X_2,\dots,X_K)$ such that $1 \leq X_i \leq N\ (1\leq i \leq K)$.

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What is bitwise $\mathrm{XOR}$? The bitwise $\mathrm{XOR}$ of non-negative integers $A$ and $B$, $A \oplus B$, is defined as follows: When $A \oplus B$ is written in base two, the digit in the $2^k$'s place ($k \geq 0$) is $1$ if exactly one of the digits in that place of $A$ and $B$ is $1$, and $0$ otherwise. For example, we have $3 \oplus 5 = 6$ (in base two: $011 \oplus 101 = 110$). Generally, the bitwise $\mathrm{XOR}$ of $k$ non-negative integers $p_1, p_2, p_3, \dots, p_k$ is defined as $(\dots ((p_1 \oplus p_2) \oplus p_3) \oplus \dots \oplus p_k)$. We can prove that this value does not depend on the order of $p_1, p_2, p_3, \dots, p_k$.

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Constraints

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  • $1 \leq N \leq 1000$
  • $1 \leq K \leq 10^{12}$
  • $0 \leq A_i \leq 1000$
  • All values in the input are integers.
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Input

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The input is given from Standard Input in the following format:

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N K
A_1 A_2 \dots A_N

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Output

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Print the answer.

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样例

Input #1
2 2
10 30
Output #1
40
There are four sequences to consider: $(X_1,X_2)=(1,1),(1,2),(2,1),(2,2)$, for which $A_{X_1}+A_{X_2}$ is $20,40,40,60$, respectively. Thus, the answer is $20 \oplus 40 \oplus 40 \oplus 60=40$.
Input #2
4 10
0 0 0 0
Output #2
0
Input #3
11 998244353
314 159 265 358 979 323 846 264 338 327 950
Output #3
236500026047
题目信息
题号
arc156_d
时间限制
2 s
内存限制
1024 MB

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