HDU-5785 Interesting（Manacher算法+区间处理）

# include<iostream>
# include<cstdio>
# include<cstring>
# include<algorithm>
using namespace std;
# define LL long long

const int mod=1000000007;
const int N=1000000;

char str[N+5];
char m[(N<<1)+5];
int p[(N<<1)+5];

LL addtag[2][N+5];
LL subtag[2][N+5];
LL addcnt[2][N+5];
LL subcnt[2][N+5];
LL val[2][N+5];

void manacher(char *ch)
{
	int len=strlen(ch+1);
	int cnt=0;
	m[cnt++]=‘@‘;
	m[cnt++]=‘#‘;
	for(int i=1;i<=len;++i){
		m[cnt++]=ch[i];
		m[cnt++]=‘#‘;
	}
	m[cnt]=‘\0‘;
	int id,mx=0;
	for(int i=1;i<cnt;++i){
		if(mx>i) p[i]=min(mx-i,p[2*id-i]);
		else p[i]=1;
		while(m[i-p[i]]==m[i+p[i]]) ++p[i];
		if(i+p[i]>mx){
			mx=i+p[i];
			id=i;
		}
	}
}

void update(int id,int l,int r,int a)
{
	addtag[id][l]+=a;
	addtag[id][l]%=mod;
	++addcnt[id][l];
	subtag[id][r+1]+=a-r+l;
	subtag[id][r+1]%=mod;
	++subcnt[id][r];
}

void pushDown(int n)
{
	for(int i=1;i<=n;++i){
		if(addcnt[0][i]){
			val[0][i]+=addtag[0][i];
			val[0][i]%=mod;
			addtag[0][i+1]+=addtag[0][i]-addcnt[0][i];
			addtag[0][i+1]%=mod;
			addcnt[0][i+1]+=addcnt[0][i];
		}
		if(subcnt[0][i]){
			val[0][i]-=subtag[0][i];
			val[0][i]%=mod;
			subtag[0][i+1]+=subtag[0][i]-subcnt[0][i];
			subtag[0][i+1]%=mod;
			subcnt[0][i+1]+=subcnt[0][i];
		}
		if(addcnt[1][i]){
			val[1][i]+=addtag[1][i];
			val[1][i]%=mod;
			addtag[1][i+1]+=addtag[1][i]-addcnt[1][i];
			addtag[1][i+1]%=mod;
			addcnt[1][i+1]+=addcnt[1][i];
		}
		if(subcnt[1][i]){
			val[1][i]-=subtag[1][i];
			val[1][i]%=mod;
			subtag[1][i+1]+=subtag[1][i]-subcnt[1][i];
			subtag[1][i+1]%=mod;
			subcnt[1][i+1]+=subcnt[1][i];
		}
	}
}

int main()
{
	while(~scanf("%s",str+1))
	{
		manacher(str);
		memset(val,0,sizeof(val));
		memset(addtag,0,sizeof(addtag));
		memset(subtag,0,sizeof(subtag));
		memset(addcnt,0,sizeof(addcnt));
		memset(subcnt,0,sizeof(subcnt));
		for(int i=1;m[i];++i){
			if(i&1){
				if(p[i]==1) continue;
				update(0,i/2+1,i/2+p[i]/2,i/2);
				update(1,i/2-p[i]/2+1,i/2,i/2+p[i]/2);
			}else{
				int id=i/2;
				int l=(p[i]-1)/2;
				update(0,id,id+l,id);
				update(1,id-l,id,id+l);
			}
		}
		int n=strlen(str+1);
		pushDown(n);
		LL ans=0;
		for(int i=1;i<n;++i){
			ans+=val[0][i]*val[1][i+1];
			ans%=mod;
		}
		while(ans<0) ans+=mod;
		printf("%lld\n",ans);
	}
	return 0;
}