二分+后缀数组
在height数组上二分
1 /************************************************************** 2 Problem: 2946 3 User: idy002 4 Language: C++ 5 Result: Accepted 6 Time:956 ms 7 Memory:1596 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <cstring> 12 #include <iostream> 13 #include <vector> 14 #define N 10010 15 using namespace std; 16 17 int tot; 18 int n, aa[N]; 19 int sa[2][N], rk[2][N], ht[N], vv[N], p, q; 20 int bel[N]; 21 bool mark[10]; 22 23 void expand( int k ) { 24 for( int i=1; i<=n; i++ ) vv[rk[p][sa[p][i]]] = i; 25 for( int i=n; i>=1; i-- ) 26 if( sa[p][i]>k ) 27 sa[q][vv[rk[p][sa[p][i]-k]]--]=sa[p][i]-k; 28 for( int i=n-k+1; i<=n; i++ ) 29 sa[q][vv[rk[p][i]]--] = i; 30 for( int i=1; i<=n; i++ ) 31 rk[q][sa[q][i]] = rk[q][sa[q][i-1]]+ 32 (rk[p][sa[q][i]]!=rk[p][sa[q][i-1]]||rk[p][sa[q][i]+k]!=rk[p][sa[q][i-1]+k]); 33 } 34 void calcht() { 35 for( int i=1,k=0; i<=n; i++ ) { 36 if( rk[p][i]==1 ) { 37 k = ht[i] = 0; 38 continue; 39 } 40 int j=sa[p][rk[p][i]-1]; 41 while( aa[i+k]==aa[j+k] ) k++; 42 ht[i] = k; 43 if( k>0 ) k--; 44 } 45 } 46 void suffix() { 47 p=1, q=0; 48 for( int i=1; i<=n; i++ ) vv[aa[i]]++; 49 for( int i=1; i<=27; i++ ) vv[i]+=vv[i-1]; 50 for( int i=n; i>=1; i-- ) sa[p][vv[aa[i]]--]=i; 51 for( int i=1; i<=n; i++ ) 52 rk[p][sa[p][i]]=rk[p][sa[p][i-1]]+(aa[sa[p][i]]!=aa[sa[p][i-1]]); 53 for( int k=1; k<n; k<<=1,swap(p,q) ) 54 expand(k); 55 calcht(); 56 } 57 bool ok( int k ) { 58 int top=1; 59 for( int i=2; i<=n; i++ ) { 60 if( ht[sa[p][i]]<k ) { 61 int cnt = 0; 62 for( int j=0; j<=n; j++ ) 63 mark[j] = false; 64 for( int j=top; j<i; j++ ) { 65 int ps = sa[p][j]; 66 if( bel[ps] && !mark[bel[ps]] ) { 67 cnt++; 68 mark[bel[ps]] = true; 69 } 70 } 71 if( cnt==tot ) return true; 72 top = i; 73 } 74 } 75 return false; 76 } 77 int sov() { 78 int lf=0, rg=2000; 79 while( lf<rg ) { 80 int mid=(lf+rg+1)>>1; 81 if( ok(mid) ) lf=mid; 82 else rg=mid-1; 83 } 84 return lf; 85 } 86 void test() { 87 const char buf[] = " abcba"; 88 n = 5; 89 for( int i=1; i<=n; i++ ) 90 aa[i] = buf[i]-'a'+1; 91 suffix(); 92 for( int i=1; i<=n; i++ ) 93 printf( "%d: %s ", ht[sa[p][i]], buf+sa[p][i] ); 94 } 95 int main() { 96 static char buf[N]; 97 scanf( "%d", &tot ); 98 for( int i=1; i<=tot; i++ ) { 99 scanf( "%s", buf ); 100 for( int j=0; buf[j]; j++ ) { 101 n++; 102 aa[n] = buf[j]-'a'+1; 103 bel[n] = i; 104 } 105 if( i!=tot ) { 106 n++; 107 aa[n] = 27; 108 bel[n] = 0; 109 } 110 } 111 suffix(); 112 printf( "%d ", sov() ); 113 }