POJ 1743 后缀数组

思路：
后缀数组论文题
对后缀分组

//By SiriusRen#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define N 20005int n,s[N],cntA[N],cntB[N],A[N],B[N],rk[N],sa[N],tsa[N],ht[N];void SA(){    memset(cntA,0,sizeof(cntA));    for(int i=1;i<=n;i++)cntA[s[i]]++;    for(int i=1;i<=200;i++)cntA[i]+=cntA[i-1];    for(int i=n;i;i--)sa[cntA[s[i]]--]=i;    rk[sa[1]]=1;    for(int i=2;i<=n;i++)rk[sa[i]]=rk[sa[i-1]]+(s[sa[i]]!=s[sa[i-1]]);    for(int l=1;rk[sa[n]]<n;l<<=1){        memset(cntA,0,sizeof(cntA));        memset(cntB,0,sizeof(cntB));        for(int i=1;i<=n;i++)            cntA[A[i]=rk[i]]++,            cntB[B[i]=i+l<=n?rk[i+l]:0]++;        for(int i=1;i<=n;i++)cntA[i]+=cntA[i-1],cntB[i]+=cntB[i-1];        for(int i=n;i;i--)tsa[cntB[B[i]]--]=i;        for(int i=n;i;i--)sa[cntA[A[tsa[i]]]--]=tsa[i];        rk[sa[1]]=1;        for(int i=2;i<=n;i++)rk[sa[i]]=rk[sa[i-1]]+(A[sa[i]]!=A[sa[i-1]]||B[sa[i]]!=B[sa[i-1]]);    }    for(int i=1,j=0;i<=n;i++){        j=j?j-1:0;        while(s[i+j]==s[sa[rk[i]-1]+j])j++;        ht[rk[i]]=j;    }}bool check(int x){    int minn=n+1,maxx=0;    for(int i=1;i<=n;i++){        if(ht[i]>=x){            minn=min(minn,sa[i]),maxx=max(maxx,sa[i]);            if(maxx-minn>x)return 1;        }        else minn=maxx=sa[i];    }return 0;}int main(){    while(scanf("%d",&n)&&n){        for(int i=1;i<=n;i++)scanf("%d",&s[i]);        for(int i=n;i;i--)s[i]=s[i]-s[i-1]+100;        SA();        int l=1,r=n,ans=0;        while(l<=r){            int mid=(l+r)>>1;            if(check(mid))l=mid+1,ans=mid;            else r=mid-1;        }        printf("%d\n",ans>=4?ans+1:0);    }}