最长重复出现的可以重叠的字串（POJ 3261）
#include <iostream> #include <cstdlib> #include <cstdio> #include <cstring> using namespace std; const int max_value=20001; int m[max_value]; int sa[max_value],lstsa[max_value]; int rank[max_value],lstrank[max_value]; int h[max_value]; int pow; int cmp1(const void * a,const void *b) { const int * x = (const int *)a; const int * y = (const int *)b; return m[*x]-m[*y]; } int cmp2(const void * a,const void * b) { const int * x= (const int *)a; const int * y = (const int *)b; if(lstrank[*x]!=lstrank[*y]) return lstrank[*x]-lstrank[*y]; else return lstrank[*x+pow]-lstrank[*y+pow]; } void suffix_array(int n) { int i=0; int j = 0; //caculate sa and rank when pow = 1; for(i=1;i<=n;i++) sa[i]=i; qsort(sa,n,sizeof(int),cmp1); for(i=1,j=0;i<=n;i++) { if(i==1 || m[sa[i]]!=m[sa[i-1]])//when there are some continous-muti,e."aabbbaa",they have the same rank j++; rank[sa[i]]=j; } //caculate sa and rank when pow<<1 using lstrank and lstsa for(pow=1;pow<=n;pow<<=1)//pow<<1 { memcpy(lstsa,sa,sizeof(int)*n); memcpy(lstrank,rank,sizeof(int)*n); qsort(sa,n,sizeof(int),cmp2); for(i=1,j=0;i<=n;i++) { if(i==1 || cmp2(&sa[i],&sa[i-1])!=0) j++; rank[sa[i]]=j; } } } //cal the LCS between rank-adjacent suff //h[i] is the LCS between suff(sa[i]) and suff(sa[i-1]) //h[rank[i]] is the LCS between suff(i) and suff(sa[[rank[i]-1]) //h[rank[i]]>=h[rank[i-1]]-1 //that means "the LCS between the suff(i) and suff(sa[rank[i]-1])" is at least "the LCS between the suff(i-1) and suff(sa[rank[i]-1])-1" //so to calculate h[rank[i]], firstly calculate h[rank[i-1]] void cal_height(int n ) { int i=0,j=0,k=0; for(i=1;i<=n;i++) { if(rank[i]==1) { h[rank[i]]=k=0; } else { if(k>0) k--;//sub the first 'char' of suff(i-1) is the suff(i) j = sa[rank[i]-1]; for(;m[i+k]==m[j+k];k++);//start from k, the cmp before k has been done when calculating h[rank[i-1]] h[rank[i]] = k; } } } /* *判断是，根据排好序的后缀，根据不同的“后缀的前缀”，sa分成多个组，每个组内都可能出现重复“前缀”，于是判断每个组长度为len重复出现的次数。当遇到一个新的组时，令c=1,重新开始。 例如:12323231,当n=8,k=2，len=2时， 1 1 2 3 2 3 2 3 1 2 3 1 2 3 2 3 1 2 3 2 3 2 3 1 3 1 3 2 3 1 3 2 3 2 3 1 上述就可以分为三组，其中第二组和第三组中都出现了符合条件的重复串。 */ //k表示次数，len表示当前测试长度 bool check(int n,int k,int len) { int c=1; int i = 0; for(i=1;i<=n;i++) { if(h[i]>=len) c++; else c=1; if(c>=k) return true; } return false; } int main() { int n ,k; scanf("%d",&n); scanf("%d",&k); int i = 0; memset(sa,0,sizeof(sa)); memset(rank,0,sizeof(rank)); memset(lstsa,0,sizeof(lstsa)); memset(lstrank,0,sizeof(lstrank)); memset(h,0,sizeof(h)); memset(m,0,sizeof(m)); for(i=1;i<=n;i++) scanf("%d",&m[i]); suffix_array(n); cal_height(n); int l=1,h=n; int mid=1; while(l<=h) { mid = l+(h-l+1)/2; if(check(n,k,mid)) l = mid+1; else h = mid-1; } printf("%d/n",h); }