URAL 1517 Freedom of Choice (后缀数组输出两个串最长公共子串)

女爷i 2022-08-24 04:16 148阅读 0赞

题意：给出两个串的长度（一样长），输出它们的任意一个最长公共子串

#include <cstdio>
    #include <cstring>
    #define max(a,b) ((a)>(b)?(a):(b))
    #define min(a,b) ((a)<(b)?(a):(b))
    
    const int N = int(2e5)+10; //两个串的总长
    
    #define F(x) ((x)/3+((x)%3==1?0:tb))
    #define G(x) ((x)<tb?(x)*3+1:((x)-tb)*3+2)
    
    int wa[N],wb[N],wv[N],ws[N];
    int c0 (int *r,int a,int b){
    	return r[a]==r[b] && r[a+1]==r[b+1] && r[a+2]==r[b+2];
    }
    int c12 (int k,int *r,int a,int b){
    	if (k==2) return r[a]<r[b] || r[a]==r[b] && c12(1,r,a+1,b+1);
    	else return r[a]<r[b] || r[a]==r[b] && wv[a+1]<wv[b+1];
    }
    void sort (int *r,int *a,int *b,int n,int m){
    	int i;
    	for(i=0;i<n;i++) wv[i]=r[a[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--) b[--ws[wv[i]]]=a[i];
    }
    void DC3 (int *r,int *sa,int n,int m){
    	int i,j,*rn=r+n,*san=sa+n,ta=0,tb=(n+1)/3,tbc=0,p;
    	r[n]=r[n+1]=0;
    	for(i=0;i<n;i++) if(i%3!=0) wa[tbc++]=i;
    	sort(r+2,wa,wb,tbc,m);
    	sort(r+1,wb,wa,tbc,m);
    	sort(r,wa,wb,tbc,m);
    	for(p=1,rn[F(wb[0])]=0,i=1;i<tbc;i++)
    		rn[F(wb[i])]=c0(r,wb[i-1],wb[i])?p-1:p++;
    	if(p<tbc) DC3(rn,san,tbc,p);
    	else for(i=0;i<tbc;i++) san[rn[i]]=i;
    	for(i=0;i<tbc;i++) if(san[i]<tb) wb[ta++]=san[i]*3;
    	if(n%3==1) wb[ta++]=n-1;
    	sort(r,wb,wa,ta,m);
    	for(i=0;i<tbc;i++) wv[wb[i]=G(san[i])]=i;
    	for(i=0,j=0,p=0;i<ta && j<tbc;p++)
    		sa[p]=c12(wb[j]%3,r,wa[i],wb[j])?wa[i++]:wb[j++];
    	for(;i<ta;p++) sa[p]=wa[i++];
    	for(;j<tbc;p++) sa[p]=wb[j++];
    }  
    int rank[N],height[N],sa[3*N],data[3*N];
    
    void calheight(int *r,int *sa,int n){
    //	memset(height,0,sizeof(height));
    //	memset(rank,0,sizeof(rank));
    	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]; r[i+k]==r[j+k]; k++);
    }
    
    int n1,n2;
    char str[N<<1];
    
    bool Judge (__int64 a,__int64 b)
    {
    	if ((a-n1)*(b-n1)<0)
    		return true;
    	return false;
    }
    
    void Deal ()
    {
    	int maxn=-1,where=0,i;
    	DC3(data,sa,n1+n2+2,'z'+1);
    	calheight(data,sa,n1+n2+1);  
    	for (i=2;i<=n1+n2+1;i++)
    		if (Judge(sa[i-1],sa[i]) && height[i]>maxn)
    		{
    			maxn=height[i];
    			where=sa[i];
    		}
    	for (i=0;i<maxn;i++)
    		str[i]=data[where+i];
    	str[i]=0;
    	printf("%s\n",str);
    }
    
    int main ()
    {
    	scanf("%d",&n1);
    	n2=n1;
    	scanf("%s",str);
    	int i;
    	for (i=0;i<n1;i++)
    		data[i]=(int)str[i];
    	data[i]=1;   //不同于串中字符的分隔符
    	scanf("%s",str);
    	for (i=0;i<n2;i++)
    		data[n1+1+i]=(int)str[i];
    	data[n1+1+i]=0;
    	Deal();
    	return 0;
    }