MZL’s xor

题目连接：

http://acm.hdu.edu.cn/showproblem.php?pid=5344

Description

MZL loves xor very much.Now he gets an array A.The length of A is n.He wants to know the xor of all (Ai+Aj)(1≤i,j≤n)
The xor of an array B is defined as B1 xor B2…xor Bn

Input

Multiple test cases, the first line contains an integer T(no more than 20), indicating the number of cases.
Each test case contains four integers:n,m,z,l
A1=0,Ai=(Ai−1∗m+z) mod l
1≤m,z,l≤5∗105,n=5∗105

Output

For every test.print the answer.

Sample Input

2
3 5 5 7
6 8 8 9

Sample Output

14
16

Hint

题意

求所有的Ai+Aj的异或值,1<=i,j<=n

题解：

ai+aj这尼玛不是FFT嘛

赶紧莽一波，然后TLE成傻逼了

然后队友提醒我了，(ai+aj)^(aj+ai)=0,其实这是一道智障题……

当时整个人都懵逼了

代码

#include<bits/stdc++.h>
using namespace std;

int n,m,z,l;
void solve()
{
    scanf("%d%d%d%d",&n,&m,&z,&l);
    long long ans = 0;
    long long pre = 0;
    for(int i=0;i<n;i++)
    {
        ans^=2LL*pre;
        pre = (1ll*pre*m+z)%l;
    }
    cout<<ans<<endl;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)solve();
    return 0;
}