狄利克雷前缀和
用法
计算：
\[s(i) = \sum_{d\mid i} f_{d}\]
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41 | #include<bits/stdc++.h>
using namespace std;
const int MAXN = 2e7 + 3;
unsigned A[MAXN];
int p, P[MAXN]; bool V[MAXN];
void solve(int n){
for(int i = 2;i <= n;++ i){
if(!V[i]){
P[++ p] = i;
for(int j = 1;j <= n / i;++ j){ // 前缀和
A[j * i] += A[j];
}
}
for(int j = 1;j <= p && P[j] <= n / i;++ j){
V[i * P[j]] = true;
if(i % P[j] == 0)
break;
}
}
}
unsigned seed;
inline unsigned read(){
seed ^= seed << 13;
seed ^= seed >> 17;
seed ^= seed << 5;
return seed;
}
int main(){
int n;
cin >> n >> seed;
for(int i = 1;i <= n;++ i){
A[i] = read();
}
solve(n);
unsigned ans = 0;
for(int i = 1;i <= n;++ i){
ans ^= A[i];
}
cout << ans << endl;
return 0;
}
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