一开始还想用o(n)贪心……想多了……
后缀数组预处理之后通过比较rank来确定取前面的或者后面的
调了半天发现c[]开小了QAQ
1 #include<algorithm> 2 #include<iostream> 3 #include<cstdlib> 4 #include<cstring> 5 #include<cstdio> 6 #include<string> 7 #include<cmath> 8 #include<ctime> 9 #include<queue> 10 #include<stack> 11 #include<map> 12 #include<set> 13 #define rre(i,r,l) for(int i=(r);i>=(l);i--) 14 #define re(i,l,r) for(int i=(l);i<=(r);i++) 15 #define Clear(a,b) memset(a,b,sizeof(a)) 16 #define inout(x) printf("%d",(x)) 17 #define douin(x) scanf("%lf",&x) 18 #define strin(x) scanf("%s",(x)) 19 #define LLin(x) scanf("%lld",&x) 20 #define op operator 21 #define CSC main 22 typedef unsigned long long ULL; 23 typedef const int cint; 24 typedef long long LL; 25 using namespace std; 26 void inin(int &ret) 27 { 28 ret=0;int f=0;char ch=getchar(); 29 while(ch<'0'||ch>'9'){if(ch=='-')f=1;ch=getchar();} 30 while(ch>='0'&&ch<='9')ret*=10,ret+=ch-'0',ch=getchar(); 31 ret=f?-ret:ret; 32 } 33 int sa[70030],c[70111],t[70030],t2[70030],rank[70030]; 34 char s[70030]; 35 void build_sa(int m) 36 { 37 int *x=t,*y=t2,n=strlen(s),p=0; 38 re(i,0,m-1)c[i]=0; 39 re(i,0,n-1)c[x[i]=s[i]]++; 40 re(i,1,m-1)c[i]+=c[i-1]; 41 rre(i,n-1,0)sa[--c[x[i]]]=i; 42 for(int k=1;k<=n;k<<=1) 43 { 44 p=0; 45 rre(i,n-1,n-k)y[p++]=i; 46 re(i,0,n-1)if(sa[i]>=k)y[p++]=sa[i]-k; 47 re(i,0,m-1)c[i]=0; 48 re(i,0,n-1)c[x[y[i]]]++; 49 re(i,1,m-1)c[i]+=c[i-1]; 50 rre(i,n-1,0)sa[--c[x[y[i]]]]=y[i]; 51 swap(x,y); 52 x[sa[0]]=0,p=1; 53 re(i,1,n-1) 54 x[sa[i]]=y[sa[i]]==y[sa[i-1]]&&y[sa[i]+k]==y[sa[i-1]+k]?p-1:p++; 55 if(p>=n)break; 56 m=p; 57 } 58 } 59 int n; 60 int main() 61 { 62 freopen("in.in","r",stdin); 63 freopen("out.out","w",stdout); 64 scanf("%d",&n); 65 re(i,0,n-1) 66 { 67 getchar(); 68 s[i]=getchar(); 69 } 70 s[n]='Z'+1; 71 re(i,0,n-1)s[(n<<1)-i]=s[i]; 72 build_sa(1000); 73 re(i,0,n<<1)rank[sa[i]]=i; 74 int l=0,r=n-1; 75 for(int tot=0;tot<n&&l<r;tot++) 76 { 77 if(tot&&tot%80==0)cout<<" "; 78 if(rank[l]<rank[(n<<1)-r])printf("%c",s[l++]); 79 else printf("%c",s[(n<<1)-(r--)]); 80 } 81 printf("%c",s[l]); 82 return 0; 83 }