HDU 5785 Interesting

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const ll M=1111111,Mod=1000000007;
char c[M],s[M<<1];
ll p[M<<1],val[2][M],ad1[2][M],ad2[2][M],re1[2][M],re2[2][M];
void init(){
	memset(p,0,sizeof(p));
    memset(val,0,sizeof(val));
    memset(ad1,0,sizeof(ad1));
    memset(ad2,0,sizeof(ad2));
    memset(re1,0,sizeof(re1));
    memset(re2,0,sizeof(re2));
}
void manacher(ll len){
    ll i,id,mx=0;
    for(i=1;i<len;i++){
        if(i<mx)p[i]=min(p[2*id-i],mx-i);
        else p[i]=1;
        while(s[i-p[i]]==s[i+p[i]])p[i]++;
        if(mx<i+p[i]){
            id=i;
            mx=i+p[i];
        }
   }
}
void add(bool d,ll l,ll r,ll k){
    ad1[d][l]=(ad1[d][l]+k)%Mod;
    ++ad2[d][l];
    re1[d][r+1]=(re1[d][r+1]+k-r+l)%Mod;
    ++re2[d][r];
}
int main(){
    ll i,n,len,ans;
    while(~scanf("%s",c)){
        ans=0;
        init();
        n=strlen(c);
        s[0]='$';s[1]='#';
        for(i=0;i<n;i++){
            s[2*i+2]=c[i];
            s[2*i+3]='#';
        }
        len=2*n+2;
        s[len]='\0';
        manacher(len);
        for(i=1;i<=len;i++)
            if(i&1){
                if(p[i]==1)continue;
                add(0,i/2-p[i]/2+1,i/2,i/2+p[i]/2);
                add(1,i/2+1,i/2+p[i]/2,i/2);
            }
            else{
                add(0,i/2-p[i]/2+1,i/2,i/2+p[i]/2-1);
                add(1,i/2,i/2+p[i]/2-1,i/2);
            }
        for(i=1;i<=n;i++){
            if(ad2[0][i]){
                val[0][i]=(val[0][i]+ad1[0][i])%Mod;
                ad1[0][i+1]=(ad1[0][i+1]+ad1[0][i]-ad2[0][i])%Mod;
                ad2[0][i+1]+=ad2[0][i];
            }
            if(re2[0][i]){
                val[0][i]=(val[0][i]-re1[0][i])%Mod;
                re1[0][i+1]=(re1[0][i+1]+re1[0][i]-re2[0][i])%Mod;
                re2[0][i+1]+=re2[0][i];
            }
            if(ad2[1][i]){
                val[1][i]=(val[1][i]+ad1[1][i])%Mod;
                ad1[1][i+1]=(ad1[1][i+1]+ad1[1][i]-ad2[1][i])%Mod;
                ad2[1][i+1]+=ad2[1][i];
            }
            if(re2[1][i]){
                val[1][i]=(val[1][i]-re1[1][i])%Mod;
                re1[1][i+1]=(re1[1][i+1]+re1[1][i]-re2[1][i])%Mod;
                re2[1][i+1]+=re2[1][i];
            }
        }
        for(i=1;i<=n-1;i++)
            ans=(ans+val[1][i]*val[0][i+1])%Mod;
		if(ans<0)ans+=Mod;
        cout<<ans<<endl;
    }
    return 0;
}