后缀数组

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define maxnode 200005
using namespace std;
int t1[maxnode]={0},t2[maxnode]={0},sa[maxnode]={0},cc[maxnode]={0},n,m=0;
char ss[maxnode];
bool cmp(int *y,int a,int b,int k)
{
    int a2,b2;
    a2= a+k>=n ? -1 : y[a+k];
    b2= b+k>=n ? -1 : y[b+k];
    a=y[a];b=y[b];
    return a==b&&a2==b2;
}
void build()
{
    int i,k,p;int *x=t1;int *y=t2;
    for (i=0;i<m;++i) cc[i]=0;
    for (i=0;i<n;++i) ++cc[x[i]=ss[i]];
    for (i=1;i<m;++i) cc[i]+=cc[i-1];
    for (i=n-1;i>=0;--i) sa[--cc[x[i]]]=i;
    for (k=1;k<=n;k<<=1)
    {
        p=0;
        for (i=n-k;i<n;++i) y[p++]=i;
        for (i=0;i<n;++i) if (sa[i]>=k) y[p++]=sa[i]-k;
        for (i=0;i<m;++i) cc[i]=0;
        for (i=0;i<n;++i) ++cc[x[y[i]]];
        for (i=1;i<m;++i) cc[i]+=cc[i-1];
        for (i=n-1;i>=0;--i) sa[--cc[x[y[i]]]]=y[i];
        swap(x,y);m=1;x[sa[0]]=0;
        for (i=1;i<n;++i) x[sa[i]]=cmp(y,sa[i],sa[i-1],k) ? m-1 : m++;
        if (m>=n) break;
    }
}
int main()
{
    int i,n1;
    scanf("%s",&ss);n1=strlen(ss);
    for (i=0;i<n1-1;++i) ss[i+n1]=ss[i]; n=n1*2-1;
    for (i=0;i<n1;++i) m=max(m,(int)ss[i]);
    ++m;build();
    for (i=0;i<n;++i)
      if (sa[i]<n1) printf("%c",ss[sa[i]+n1-1]);
    printf("\n");
}