UVALive - 7041 The Problem to Slow Down You （回文树）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
#include <ctime>
#include <vector>
#include <queue>
#include <map>
#include <stack>
#include <set>
#include <bitset>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define ms(a, b) memset(a, b, sizeof(a))
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
//#define eps 0.0000000001
#define IOS ios::sync_with_stdio(0);cin.tie(0);
#define random(a, b) rand()*rand()%(b-a+1)+a
#define pi acos(-1)
//const ll INF = 0x3f3f3f3f3f3f3f3fll;
const int inf = 0x3f3f3f3f;
const int maxn = 2e5 + 10;
const int maxm = 3000000 +10;
const int mod = 1000000007;

struct PAM{
    int nxt[maxn][26];
    int fail[maxn];
    int cnt[maxn];
    int num[maxn];
    int len[maxn];
    int s[maxn];
    int last,n,p;

    int newnode(int w){
        for(int i=0;i<26;i++) nxt[p][i]=0;
        num[p]=cnt[p]=0;
        len[p]=w;
        return p++;
    }
    void init(){
        n=last=p=0;
        newnode(0);
        newnode(-1);
        s[n]=-1;
        fail[0]=1;
    }
    int get_fail(int x){
        while(s[n-len[x]-1]!=s[n]) x=fail[x];
        return x;
    }
    void add(int c){
        c-=‘a‘;
        s[++n]=c;
        int cur=get_fail(last);
        if(!nxt[cur][c]){
            int now=newnode(len[cur]+2);
            fail[now]=nxt[get_fail(fail[cur])][c];
            nxt[cur][c]=now;
            num[now]=num[fail[now]]+1;
        }
        last=nxt[cur][c];
        cnt[last]++;
    }
    void Count(){
        for(int i=p-1;i>=0;i--) cnt[fail[i]]+=cnt[i];
    }
};
PAM pam1,pam2;
char a[maxn],b[maxn];
ll dfs(int an,int bn){
    ll res=0;
    for(int i=0;i<26;i++)
        if(pam1.nxt[an][i]!=0&&pam2.nxt[bn][i]!=0){
            res+=(ll)pam1.cnt[pam1.nxt[an][i]]*pam2.cnt[pam2.nxt[bn][i]]+dfs(pam1.nxt[an][i],pam2.nxt[bn][i]);
        }
    return res;
}
int main() {
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
//    freopen("input.txt", "w", stdout);
#endif
    int T,cas=1;
    scanf("%d",&T);

    while(T--){
        pam1.init();
        pam2.init();
        scanf("%s%s",a,b);
        int l1=strlen(a),l2=strlen(b);
        for(int i=0;i<l1;i++) pam1.add(a[i]);
        for(int i=0;i<l2;i++) pam2.add(b[i]);
        pam1.Count();
        pam2.Count();
        ll ans=dfs(0,0)+dfs(1,1);
        printf("Case #%d: %lld\n",cas++,ans);
    }
    return 0;
}