Suffix array: Construct a suffix array, and note that you want to add a character that does not appear at the end of the string. Then it can be 2 points or direct scan, the direct scan needs to use the monotone queue to maintain
VIEW CODE
#include <cstdio> #include <algorithm> #include <iostream> #include <cmath> #include <queue > #include <stack> #include <string> #include <cstring> #include <map> #include <vector > #include <set> #include <ctime> #include <stdlib.h>using namespace Std;const int mmax= 40010;const int mod=1000000007;typedef Long Long ll;//typedef unsigned long long ull;char s[mmax];int sa[mmax],t[mmax],t2[mmax],c[ Mmax],n;void build_sa (int m) {int i,*x=t,*y=t2; for (i=0;i<m;i++) c[i]=0; for (i=0;i<n;i++) c[x[i]=s[i]]++; for (i=1;i<m;i++) c[i]+=c[i-1]; for (i=n-1;i>=0;i--) sa[--c[x[i]]]=i; for (int k=1;k<=n;k<<=1) {int 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++) c[i]=0; for (i=0;i<n;i++) c[x[y[i]]]++; for (i=1;i<m;i++) c[i]+=c[i-1]; for (i=n-1;i>=0;i--) sa[--c[x[y[i]]]]=y[i]; Swap (x, y); p=1;x[sa[0]]=0; for (i=1;i<n;i++) x[sa[i]] = Y[sa[i-1]]==y[sa[i]] && y[sa[i-1]+k]==y[sa[i]+k]?p-1:p++; if (p>=n) break; M=p; }}int rank[mmax],heigth[mmax];void Getheigth () {for (int i=0;i<n;i++) rank[sa[i]]=i; int k=0; for (int i=0;i<n;i++) {if (k) k--; if (Rank[i]) {int j=sa[rank[i]-1]; while (S[i+k]==s[j+k]) k++; Heigth[rank[i]]=k; }}}int len[mmax];int mark[mmax];int head,end,head1,end1;int main () {int m; while (scanf ("%d", &m) &&m) {head=end=0; head1=end1=0; scanf ("%s", s); if (m==1) {printf ("%d%d\n", strlen (s), 0); Continue } n=strlen (s); S[n++]= ' $ '; s[n]=0; BUILD_SA (131); Getheigth (); for (int i=1;i<m;i++) {while (End>head && heigth[len[end-1]]>= heigth[i]) end--; LeN[end++]=i; while (End1>head1 && Sa[mark[end1-1]] <sa[i]) end1--; Mark[end1++]=i; } int Ans=heigth[len[head]]; int E=sa[mark[head1]]; for (int i=m;i<n;i++) {if (I-m+1==len[head]) head++; while (End>head && heigth[len[end-1]]>= heigth[i]) end--; Len[end++]=i; if (I-m==mark[head1]) head1++; while (End1>head1 && Sa[mark[end1-1]] <sa[i]) end1--; Mark[end1++]=i; if (Heigth[len[head]]>ans) {Ans=heigth[len[head]]; E=SA[MARK[HEAD1]]; } else if (Heigth[len[head]]==ans) E=max (E,sa[mark[head1]]); } if (ans==0) {puts ("none"); Continue } printf ("%d%d\n", ans,e); } return 0;}
String hash: Direct 2 points well written.
VIEW CODE
#include <cstdio> #include <algorithm> #include <iostream> #include <cmath> #include <queue > #include <stack> #include <string> #include <cstring> #include <map> #include <vector > #include <set> #include <ctime> #include <stdlib.h>using namespace std;const int mmax= 1000010; const int Mod=1000000007;const int inf=0x3fffffff;using namespace std;typedef long long ll;typedef unsigned long long ULL ; ULL h[mmax];map<ull,int>q;int M;char Str[mmax]; ULL pow[mmax];void Build_ha () {int n=strlen (str); h[n]=0; for (int i=n-1;i>=0;i--) h[i]=h[i+1]*131+str[i];} ULL ha[mmax];bool ok (int k) {int n=strlen (str); for (int i=0;i+k-1<n;i++) {ULL tmp=h[i]-h[i+k]*pow[k]; ha[i]=tmp; } sort (ha,ha+n-k+1); int cnt=0; for (int i=0;i<n-k+1;i++) {if (I && ha[i]==ha[i-1]) cnt++; else {if (cnt>=m) return 1; Cnt=1;}} if (cnt>=m) return 1; return 0;} int main () {pow[0]=1; for (int i=1;i<mmax;i++) pow[i]=pow[i-1]*131; while (cin>>m&&m) {scanf ("%s", str); int N=strlen (str); int l=1,r=n+1; Build_ha (); while (l<r) {int mid= (L+R) >>1; if (OK (mid)) l=mid+1; else R=mid; } int ans=r-1; if (!ans) {puts ("none"); Continue } int e; Q.clear (); for (int i=0;i+ans-1<n;i++) {ULL Tmp=h[i]-h[i+ans]*pow[ans]; q[tmp]++; if (q[tmp]>=m) e=i; } printf ("%d%d\n", ans,e); } return 0;}
POJ 3882 (stammering aliens) suffix array or hash