[线段树 单调栈] UNR #1 争夺圣杯

争夺圣杯

#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
typedef pair<int,int> abcd;
typedef long long ll;

inline char nc()
{
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}

inline void read(int &x)
{
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

const int N=1000005;
const ll P=998244353;

ll A[N<<2],B[N<<2];
ll ia,ib; int ql,qr;

inline void modify(int rt,int l,int r)
{
if (ql<=l && r<=qr){
A[rt]+=ia; B[rt]+=ib;
if (A[rt]>P) A[rt]-=P;
if (B[rt]>P) B[rt]-=P;
return;
}
int mid=(l+r)>>1;
if (ql<=mid)
modify(rt<<1,l,mid);
if (qr>mid)
modify(rt<<1|1,mid+1,r);
}

int t; ll ret;

inline void Query(int rt,int l,int r){
ret+=A[rt]*t+B[rt];
if (ret>P) ret%=P;
if (l==r) return;
int mid=(l+r)>>1;
if (t<=mid)
Query(rt<<1,l,mid);
else
Query(rt<<1|1,mid+1,r);
}

int n,a
;
int Stack
,pnt;
int left
,right
;
ll ans;

int main()
{
freopen("t.in","r",stdin);
freopen("t.out","w",stdout);
read(n);
for (int i=1;i<=n;i++) read(a[i]);
a[0]=1<<30;
pnt=0; Stack[++pnt]=0;
for (int i=1;i<=n;i++)
{
while (a[Stack[pnt]]<a[i]) pnt--;
left[i]=Stack[pnt]+1;
Stack[++pnt]=i;
}
a[n+1]=1<<30;
pnt=0; Stack[++pnt]=n+1;
for (int i=n;i;i--)
{
while (a[Stack[pnt]]<=a[i]) pnt--;
right[i]=Stack[pnt]-1;
Stack[++pnt]=i;
}
for (int i=1;i<=n;i++)
{
int ld=i-left[i]+1,rd=right[i]-i+1;
if (ld<rd) swap(ld,rd);
ql=1,qr=rd-1;
ia=a[i]; ib=0;
if (ql<=qr)
modify(1,1,n);
ql=rd,qr=ld;
ia=0; ib=(ll)a[i]*rd%P;
if (ql<=qr)
modify(1,1,n);
ql=ld+1,qr=ld+rd-1;
ia=P-a[i]%P; ib=(ll)(ld+rd)*a[i]%P;
if (ql<=qr)
modify(1,1,n);
}
for (int i=1;i<=n;i++)
{
ret=0; t=i;
Query(1,1,n);
ans^=ret;
}
printf("%lld\n",ans);
return 0;
}