URAL/1517

来自"NOCOW"

可恶的后缀数组。。。

哎，看09年罗穗骞的论文吧~

#include <cstdio>
#include <cstring>
#define maxn 200010
char s[maxn];
int n,m,sa[maxn],rank[maxn],height[maxn];
int wa[maxn],wb[maxn],ws[maxn],wv[maxn];
inline bool cmp(int *r,int a,int b,int l)
{
    return (r[a] == r[b]) && (r[a+l] == r[b+l]);
}
inline void da(int n,int m)
{
    int i,j,p,*x=wa,*y=wb,*t;
    memset(ws,0,sizeof(ws));
    for (i=0;i<n;++i)  ws[x[i]=s[i]]++;
    for (i=1;i<m;++i)  ws[i]+=ws[i-1];
    for (i=n-1;i>=0;--i)  sa[--ws[x[i]]]=i;
    for (j=1,p=1;p<n;j<<=1,m=p)
    {
        for (p=0,i=n-j;i<n;++i)  y[p++]=i;
        for (i=0;i<n;++i)  if (sa[i] >= j)  y[p++]=sa[i]-j;
        for (i=0;i<n;++i)  wv[i]=x[y[i]];
        for (i=0;i<m;++i)  ws[i]=0;
        for (i=0;i<n;++i)  ws[wv[i]]++;
        for (i=1;i<m;++i)  ws[i]+=ws[i-1];
        for (i=n-1;i>=0;--i)  sa[--ws[wv[i]]]=y[i];
        for (t=x,x=y,y=t,p=1,x[sa[0]]=0,i=1;i<n;++i)
            x[sa[i]]=cmp(y,sa[i-1],sa[i],j)?p-1:p++;
    }
}
inline void calcheight()
{
    int i,j,k=0;
    for (i=1;i<=n;++i)  rank[sa[i]]=i;
    for (i=0;i<n;height[rank[i++]]=k)
    for (k?k--:0,j=sa[rank[i]-1];s[i+k]==s[j+k];k++);
}
int main()
{
    scanf("%d",&m);
    scanf("%s%s",s,s+m+1);
    s[m]=1;
    n=m+m+1;
    da(n+1,255);
    calcheight();
    int ans=0,tmp;
    for (int i=2;i<=n;++i)
        if (height[i] > ans)
            if (((m < sa[i-1]) && (m > sa[i]))
                || ((m > sa[i-1]) && (m < sa[i])))
                    ans=height[i],tmp=sa[i];
    s[tmp+ans]='\0';
    printf("%s\n",s+tmp);
    return 0;
}
//哎哎,还是写倍增算法算啦~dc3不会呢~