URAL 1517 Freedom of Choice(后缀数组，最长公共字串)

#define maxn 200010
int wa[maxn],wb[maxn],wv[maxn],ws[maxn];
int cmp(int *r,int a,int b,int l)
{return r[a]==r[b]&&r[a+l]==r[b+l];}//yuan lai zhi qian ba zhe li de l cuo dang cheng 1 le ...
void da(int *r,int *sa,int n,int m)
{
    int i,j,p,*x=wa,*y=wb,*t;
    for(i=0;i<m;i++)ws[i]=0;
    for(i=0;i<n;i++)ws[x[i]=r[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*=2,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++;
    }
}
int rankk[maxn],height[maxn];
void calheight(int *r,int *sa,int n)
{
    int i,j,k=0;
    for(i=1;i<=n;i++)rankk[sa[i]]=i;
    for(i=0;i<n;height[rankk[i++]]=k)
        for(k? k--:0,j=sa[rankk[i]-1];r[i+k]==r[j+k];k++);
}
int RMQ[maxn];
int mm[maxn];
int best[20][maxn];
void initRMQ(int n)
{
    int i,j,a,b;
    for(mm[0]=-1,i=1;i<=n;i++)
        mm[i]=((i&(i-1))==0) ? mm[i-1]+1:mm[i-1];
    for(i=1;i<=n;i++)best[0][i]=i;
    for(i=1;i<=mm[n];i++)
        for(j=1;j<=n+1-(1<<i);j++)
        {
            a=best[i-1][j];
            b=best[i-1][j+(1<<(i-1))];
            if(RMQ[a]<RMQ[b])best[i][j]=a;
            else best[i][j]=b;
        }
}
int askRMQ(int a,int b)
{
    int t;
    t=mm[b-a+1];b-=(1<<t)-1;
    a=best[t][a];b=best[t][b];
    return RMQ[a]<RMQ[b]? a:b;
}
int lcp(int a,int b)
{
    int t;
    a=rankk[a]; b=rankk[b];
    if(a>b) {t=a;a=b;b=t;}
    return (height[askRMQ(a+1,b)]);
}

    char s[maxn];
    int r[maxn],sa[maxn];
int main()
{
    int t;
    while(scanf("%d",&t)!=EOF)
    {
        scanf("%s",s);
        int len1=strlen(s);
        s[len1]=‘0‘;//yin wei bu ce ng chu xian ,suo yi bu yong dan xin ying xiang jie guo
        scanf("%s",s+len1+1);
        int len2=strlen(s);

        for(int i=0;i<len2;i++)r[i]=s[i];//r[i]biao shi pai de shi di ji
        r[len2]=0;//ji shu pai xu shi de xu yao ,zui hou yi ge jia she wei zui xiao

        da(r,sa,len2+1,130);
        calheight(r,sa,len2);
        int ans=0,be=-1;
        //bian li height shu zu, cong di 2 ge kai shi (xia biao shi cong 1 kai shi de )
        for(int i=2;i<=len2;i++)
        {
            if(height[i]>ans)
            {
                if((len1<sa[i]&&len1>sa[i-1])||(len1>sa[i]&&len1<sa[i-1]))
                {
                    ans=height[i];be=sa[i];
                }
            }
        }
        if(be!=-1)
            for(int i=be;i<be+ans;i++)printf("%c",s[i]);
        printf("\n");
    }
    return 0;
}