5.17pkusc模拟赛4

A.
B.求只存在简单环的最小环。(5.17)

#include<iostream>#include<cstdio>#include<cstring>#define N 5000#define M 10000using namespace std;struct E{int to,nxt;}edge[M*2];bool vis[N];int dis[N];int idx[N],tot,ans,T,n,m;void addedge(int from,int to){    edge[tot].to=to;edge[tot].nxt=idx[from];idx[from]=tot++;}void dfs(int x,int fa){    vis[x]=1;    dis[x]=dis[fa]+1;    for(int t=idx[x];t;t=edge[t].nxt){        E e=edge[t];        if(!vis[e.to]&&e.to!=fa) dfs(e.to,x);         if(vis[e.to]&&e.to!=fa) ans=max(ans,dis[x]-dis[e.to]+1);    }}int main(){    freopen("in.txt","r",stdin);    freopen("out.txt","w",stdout);    scanf("%d",&T);    while(T--){        memset(vis,0,sizeof(vis));        memset(dis,0,sizeof(dis));        memset(idx,0,sizeof(idx));tot=1;ans=0;        scanf("%d%d",&n,&m);        for(int i=1;i<=m;i++){            int x,y;            scanf("%d%d",&x,&y);            addedge(x,y);addedge(y,x);        }        dis[1]=1;dfs(1,0);printf("%d\n",ans);    }    return 0;}

C.n个字符串中出现在一半以上次数的最长子串。(n<=100,maxl<=1000)(5.18)
拼接在一起，利用后缀数组的height二分答案。

#include<cstdio>#include<cstring>#include<algorithm>#include<vector>#define N 200005#define pa pair<int,int>#define mp make_pair using namespace std;char tmp[N],ch[10];int t1[N],t2[N],c[N],s[N];int height[N],sa[N],r[N];int n,t,flag[N],id[N],last[N];vector<pa>vec,ans;vector<pa>::iterator it;void init(){    memset(t1,0,sizeof(t1));    memset(t2,0,sizeof(t2));    memset(c,0,sizeof(c));    memset(height,0,sizeof(height));    memset(sa,0,sizeof(sa));    memset(r,0,sizeof(r));    memset(flag,0,sizeof(flag));    memset(id,0,sizeof(id));    memset(last,0,sizeof(last));    memset(s,0,sizeof(s));}void buildsa(int m){    int *x=t1,*y=t2;    for(int i=1;i<=m;i++) c[i]=0;    for(int i=1;i<=n;i++) c[x[i]=s[i]]++;    for(int i=1;i<=m;i++) c[i]+=c[i-1];    for(int i=n;i>=1;i--) sa[c[x[i]]--]=i;    for(int k=1;k<=n;k<<=1){        int p=0;        for(int i=n-k+1;i<=n;i++) y[++p]=i;        for(int i=1;i<=n;i++) if(sa[i]>k) y[++p]=sa[i]-k;        for(int i=1;i<=m;i++) c[i]=0;        for(int i=1;i<=n;i++) c[x[y[i]]]++;        for(int i=1;i<=m;i++) c[i]+=c[i-1];        for(int i=n;i>=1;i--) sa[c[x[y[i]]]--]=y[i];        swap(x,y);p=1;x[sa[1]]=1;        for(int i=2;i<=n;i++)            x[sa[i]]=y[sa[i]]==y[sa[i-1]]&&y[sa[i]+k]==y[sa[i-1]+k]?p:++p;        if(p>=n) break;        m=p;    }}void getheight(){    for(int i=1;i<=n;i++) r[sa[i]]=i;    int i,j,k=0;    for(i=1;i<=n;i++){        if(k) k--;        int j=sa[r[i]-1];        while(s[i+k]==s[j+k]) k++;        height[r[i]]=k;    }}void cat(char *s1,char *s2){    int l=strlen(s1+1);    for(int i=l+1;s2[i-l-1];i++)        s1[i]=s2[i-l-1];}bool judge(int x){    int node=0,counter=0,l=0;    memset(flag,0,sizeof(flag));    memset(last,0,sizeof(last));    vec.clear();    for(int i=2;i<=n+1;i++){        if(height[i]>=x) {            int ii=sa[i],jj=sa[i-1];            if(!flag[id[jj]]){                counter++;                flag[id[jj]]=1;                last[id[jj]]=l;                l=id[jj];            }            if(!flag[id[ii]]){                counter++;                flag[id[ii]]=1;                last[id[ii]]=l;                l=id[ii];            }        }        if(height[i]<x) {            if(counter*2>t)vec.push_back(mp(sa[i-1],x));            while(l){                flag[l]=0;                int tmp=l;l=last[l];                last[tmp]=0;            }            counter=0;        }    }    vector<pa>::iterator it;    if(vec.size()){        ans.clear();        for(it=vec.begin();it!=vec.end();it++) {            pa x=*it;            ans.push_back(x);        }        return 1;    }    return 0;}int main(){    freopen("in.txt","r",stdin);    freopen("out.txt","w",stdout);    while(scanf("%d",&n)&&n!=0){        init();        t=n;int cnt=1,wtf=0;        scanf("%s",tmp);        for(int i=0;tmp[i];i++) s[++wtf]=tmp[i];        for(int i=2;i<=n;i++){            scanf("%s",tmp);            if(i<'a') s[++wtf]=i;            else s[++wtf]=i+30;            for(int i=0;tmp[i];i++) s[++wtf]=tmp[i];        }        n=wtf;        for(int i=1;i<=n;i++){            if(s[i]<'a'||s[i]>'z') cnt++;            else id[i]=cnt;        }        buildsa(200);        getheight();        int l=0,r=N;//      for(int i=1;i<=n;i++)//          if(s[i]<'a'||s[i]>'z')printf("%d\n",s[i]);          while(l<r){            int mid=(l+r)>>1;            if(judge(mid)) l=mid+1;             else r=mid;        }        if(l==0) {printf("?\n\n");continue;}        vector<pa>::iterator it;        for(it=ans.begin();it!=ans.end();it++){            pa x=*it;            for(int i=1;i<=x.second;i++)                printf("%c",s[x.first+i-1]);            printf("\n");        }printf("\n");    }    return 0;}

D.
E.
F.