bzoj1031: [JSOI2007]字符加密Cipher

传送门:http://www.lydsy.com:808/JudgeOnline/problem.php?id=1031

思路:非常水的后缀数组,把串复制一遍到后面,后缀排序即可。

#include<cstdio>
#include<cstring>
#include<algorithm>
const int maxn=200010;
using namespace std;
int n,t1[maxn],t2[maxn],sa[maxn],rank[maxn],sum[maxn],cnt;char s[maxn];

void getsa(){
	int *x=t1,*y=t2,m=255,p=0;
	for (int i=1;i<=n;i++) sum[x[i]=s[i]]++;
	for (int i=1;i<=m;i++) sum[i]+=sum[i-1];
	for (int i=n;i;i--) sa[sum[x[i]]--]=i;
	for (int j=1;p<n;j<<=1,m=p){
		p=0;
		for (int i=n-j+1;i<=n;i++) y[++p]=i;
		for (int i=1;i<=n;i++) if (sa[i]>j) y[++p]=sa[i]-j;
		memset(sum,0,sizeof(sum));
		for (int i=1;i<=n;i++) sum[x[y[i]]]++;
		for (int i=1;i<=m;i++) sum[i]+=sum[i-1];
		for (int i=n;i;i--) sa[sum[x[y[i]]]--]=y[i];
		swap(x,y),x[sa[1]]=p=1;
		for (int i=2;i<=n;i++){
			if (y[sa[i]]!=y[sa[i-1]]||y[sa[i]+j]!=y[sa[i-1]+j]) p++;
			x[sa[i]]=p;
		}
	}
	memcpy(rank,x,sizeof(rank));
}

int main(){
	scanf("%s",s+1),n=strlen(s+1);
	for (int i=1;i<=n;i++) s[i+n]=s[i];
	s[(n=n*2)+1]='\0',getsa(),n/=2;
	for (int i=1;i<=n*2;i++) if (sa[i]<=n) putchar(s[sa[i]+n-1]);
	puts("");
	return 0;
}


posted @ 2015-08-13 17:06  orzpps  阅读(91)  评论(0编辑  收藏  举报