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

版权声明：本文为博主原创文章，未经博主同意不得转载。 https://blog.csdn.net/whyorwhnt/article/details/34075603

题意：给出两个串的长度（一样长），输出它们的随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;
}