BZOJ4032: [HEOI2015]最短不公共子串

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=4032

SAM+序列自动机。。（其实我只是来贴模版的TAT

构造出两个字符串的SAM和序列自动机然后宽搜一遍就可以了（这是个拓扑图。。

#include<cstring>
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<queue>
#define rep(i,l,r) for (int i=l;i<=r;i++)
#define down(i,l,r) for (int i=l;i>=r;i--)
#define clr(x,y) memset(x,y,sizeof(x))
#define maxn 4005
#define ll long long
#define inf int(1e9)
using namespace std;
char sa[maxn],sb[maxn];
int f[maxn][maxn];
int n,m;
int read(){
    int x=0,f=1; char ch=getchar();
    while (!isdigit(ch)) {if (ch=='-') f=-1; ch=getchar();}
    while (isdigit(ch)) {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
struct data{
    struct sam{int l,fa,ch[30];} sam[maxn];
    int tot,root,last,head[30];
    void init(){
        clr(sam,0); tot=1; clr(head,0);
    }
    void extend(int c){
        int p,np,q,nq;
        p=last,np=++tot; last=np;
        sam[np].l=sam[p].l+1;
        for (;p&&!sam[p].ch[c];p=sam[p].fa) sam[p].ch[c]=np;
        if (!p) sam[np].fa=1;
        else {
            q=sam[p].ch[c];
            if (sam[p].l+1==sam[q].l) sam[np].fa=q;
            else {
                nq=++tot; sam[nq].l=sam[p].l+1;
                memcpy(sam[nq].ch,sam[q].ch,sizeof(sam[q].ch));
                sam[nq].fa=sam[q].fa;
                sam[np].fa=sam[q].fa=nq;
                for (;sam[p].ch[c]==q;p=sam[p].fa) sam[p].ch[c]=nq;
            }
        }
    }
    void sambuild(int n,char s[]){
        init();
        tot=last=1; 
        rep(i,1,n) extend(s[i]-'a');
    }
    void quebuild(int n,char s[]){
        int o,p,c;
        init();
        rep(i,0,25) head[i]=1;
        rep(i,1,n){
            o=++tot; c=s[i]-'a';
            rep(j,0,25) for (p=head[j];p&&!sam[p].ch[c];p=sam[p].fa) sam[p].ch[c]=o;    
              sam[o].fa=head[c];     head[c]=o;
        }
    }
} A,B;
struct node{int x,y;};
int solve(){
    queue<node> q; clr(f,0);
    q.push((node){1,1}); f[1][1]=0;
    while (!q.empty()){
        int ux=q.front().x,uy=q.front().y; q.pop();
        rep(i,0,25){
            if (!A.sam[ux].ch[i]) continue;
            if (!B.sam[uy].ch[i]) return f[ux][uy]+1;
            int vx=A.sam[ux].ch[i],vy=B.sam[uy].ch[i];
            if (!f[vx][vy]) q.push((node){vx,vy}),f[vx][vy]=f[ux][uy]+1;
        }
    }
    return -1;
}
int main(){
    scanf("%s",sa+1); scanf("%s",sb+1);
    n=strlen(sa+1); m=strlen(sb+1);
    A.sambuild(n,sa); B.sambuild(m,sb);
    printf("%d\n",solve());
    B.quebuild(m,sb);
    printf("%d\n",solve());
    A.quebuild(n,sa); B.sambuild(m,sb);
    printf("%d\n",solve());
    B.quebuild(m,sb);
    printf("%d\n",solve());
    return 0;
}