2017.10.23 模拟赛

题目链接

T1

模拟

#include <algorithm>
#include <cstring>
#include <cstdio>
#define N 100005
struct node
{
    int x,y;
    bool operator<(node a)const
    {
        return x<a.x;
    }
}pp[N];
int len,sum,tot=1;
char str[N];
int main(int argc,char *argv[])
{
    freopen("cross.in","r",stdin);
    freopen("cross.out","w",stdout);
    scanf("%s",str+1);
    len=strlen(str+1);
    for(register int i=0;i<=25;++i)
    {
        for(register int j=1;j<=len;++j)
        {
            if(i==str[j]-'a')
            {
                if(pp[tot].y) pp[++tot].x=j;
                else
                {
                    if(!pp[tot].x) pp[tot].x=j;
                    else pp[tot].y=j;
                }
            }
        }
    }
    std::sort(pp+1,pp+1+tot);
    for(register int i=1;i<=tot;++i)
    {
        int x1=pp[i].x,y1=pp[i].y;
        for(register int j=i+1;j<=tot;++j)
        {
            int x2=pp[j].x,y2=pp[j].y;
            if(x2>y1) break;
            if((x2>x1&&x2<y1&&y2>y1)) sum++;
        }
    }
    printf("%d\n",sum);
    fclose(stdin); fclose(stdout);
    return 0;
}

 

T2

二分+dijkstra 85分

正解不知道是啥

#include <cstring>
#include <cstdio>
#include <queue>
#define N 4005
#define inf 0x3f3f3f3f
using namespace std;
bool vis[N<<1],tp[505][505];
int n,m,q,k,cnt,ans=inf,far[N],to[N<<1],pre[N],head[N<<1],nextt[N<<1],val[N<<1],opt[N<<1];
struct node
{
    int x,y;
    bool operator<(node a)const
    {
        return y>a.y;
    }
};
priority_queue<node>Q;
inline int min(int a,int b) {return a>b?b:a;}
bool check(int x)
{
    int use=0;
    for(register int i=1;i<=n;++i) vis[i]=false,far[i]=inf;
    far[1]=0;
    Q.push((node){1,far[1]});
    for(node now;!Q.empty();)
    {
        now=Q.top();Q.pop();
        if(vis[now.x]) continue;
        vis[now.x]=true;
        for(register int i=head[now.x];i;i=nextt[i])
        {
            int v=to[i];
            if(far[v]>far[now.x]+val[i]&&opt[i]==1)
            {
                far[v]=far[now.x]+val[i];
                pre[v]=now.x;
                if(!vis[v]) Q.push((node){v,far[v]});
            }
            else if(far[v]>far[now.x]+val[i]&&opt[i]==2&&val[i]<=x)
            {
                far[v]=far[now.x]+val[i];
                pre[v]=now.x;
                if(!vis[v]) Q.push((node){v,far[v]});
            }
        }
    }
    for(register int i=n;pre[i];i=pre[i]) if(tp[pre[i]][i]) use++;
    if(use<=k) {ans=min(ans,far[n]);return true;}
    return false;
}
int main(int argc,char *argv[])
{
    freopen("move.in","r",stdin);
    freopen("move.out","w",stdout);
    scanf("%d%d%d%d",&n,&m,&q,&k);
    for(int u,v,w;m--;)
    {
        scanf("%d%d%d",&u,&v,&w);
        nextt[++cnt]=head[u];to[cnt]=v;val[cnt]=w;
        head[u]=cnt;opt[cnt]=1;
    }
    for(int u,v,w;q--;)
    {
        scanf("%d%d%d",&u,&v,&w);
        nextt[++cnt]=head[u];to[cnt]=v;val[cnt]=w;
        head[u]=cnt;opt[cnt]=2;
        tp[u][v]=1;
    }
    if(!k) {check(0) ;printf("%d\n",ans);return 0;} 
    int l=0,r=inf;
    for(register int mid;l<=r;)
    {
        mid=(l+r)>>1;
        if(check(mid)) l=mid+1;
        else r=mid-1;
    }
    printf("%d\n",ans);
    fclose(stdin);fclose(stdout);
    return 0;
}

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <queue>
#include <vector>

using namespace std;

namespace Solve
{
    typedef pair<int,int> Node;
    const int MAXN = 500 + 10, MAXM = 2000 + 10, INF = 0x7fffffff/2;
    int n, m, q, k;
    int nodes[MAXN][MAXN], nop;
    int head[MAXN*MAXN], next[MAXN*MAXM*2], to[MAXN*MAXM*2], w[MAXN*MAXM*2], op;
    int dis[MAXN*MAXN];

    void build(int a, int b, int x)
    {
        next[++op]=head[a];head[a]=op;to[op]=b;w[op]=x;
    }
    int dijkstra(int s, int t, int n)
    {
        priority_queue<Node, vector<Node>, greater<Node> > que;
        
        for(int i=1;i<=n;i++) dis[i] = INF;
        dis[s] = 0;
        que.push(Node(dis[s], s));
        while(!que.empty())
        {
            Node u = que.top(); que.pop();
            if (dis[u.second] != u.first) continue;
            for(int pos=head[u.second]; pos; pos=next[pos])
            {
                if (u.first + w[pos] < dis[to[pos]])
                {
                    dis[to[pos]] = u.first + w[pos];
                    que.push(Node(dis[to[pos]], to[pos]));
                }
            }
        }

        return dis[t] == INF ? -1 : dis[t];
    }
    void solve()
    {
        scanf("%d%d%d%d", &n, &m, &q, &k);
        k = min(k, n);

        nop = 0;
        for(int i=0;i<=k;i++)
            for(int u=1;u<=n;u++)
                nodes[i][u] = ++nop;

        for(int i=1;i<=m;i++)
        {
            int u, v, w;
            scanf("%d%d%d", &u, &v, &w);
            for(int j=0;j<=k;j++)
                build(nodes[j][u], nodes[j][v], w);
        }

        for(int i=1;i<=q;i++)
        {
            int x, y, z;
            scanf("%d%d%d", &x, &y, &z);
            for(int j=0;j<k;j++)
                build(nodes[j][x], nodes[j+1][y], z);
        }

        for(int i=0;i<k;i++)
            build(nodes[i][n], nodes[i+1][n], 0);
        
        cout << dijkstra(nodes[0][1], nodes[k][n], nop) << endl;
    }
}

int main()
{
    freopen("move.in", "r", stdin);
    freopen("move.out", "w", stdout);

    Solve::solve();

    return 0;
}

 

T3

20分乱搞

正解树形dp

#include <cstring>
#include <cstdio>
#include <set>
#define N 5005
#define Mod 786433

using namespace std;
set<int>se;
struct node
{
    int x,y;
}e[N];
bool V[N<<1],fw[N];
int n,k,cnt=1,tim,tot,ans,num[N<<1],id[N<<1],fa[N],to[N<<1],siz[N<<1],head[N],nextt[N<<1];
void Dfs1(int x,int pre)
{
    siz[x]=1;
    fw[x]=true;
    for(int i=head[x];i;i=nextt[i])
    {
        int v=to[i];
        if(v==pre||fw[v]) continue;
        Dfs1(v,x);
        siz[x]+=siz[v];
    }
}
void Dfs2(int x,int pre)
{
    fw[x]=true;
    for(int i=head[x];i;i=nextt[i])
    {
        int v=to[i];
        if(siz[v]>=k&&!V[id[i^1]]&&!V[id[i]]) num[++tot]=id[i],V[id[i]]=true,V[id[i^1]]=true;
        if(v==pre||fw[v]) continue;
        Dfs2(v,x);
    }
}
int find_(int x) {return x==fa[x]?x:fa[x]=find_(fa[x]);}
bool check()
{
    int Size[N];
    for(int i=1;i<=n;++i) fa[i]=i,Size[i]=0;
    for(int i=1;i<n;++i)
    {
        if(se.find(i)!=se.end()) continue;
        fa[find_(e[i].y)]=find_(e[i].x);
    }
    for(int i=1;i<=n;++i) Size[fa[find_(i)]]++;
    for(int i=1;i<=n;++i)
        if(Size[fa[find_(i)]]<k) return false;
    return true; 
}
void Dfs3(int p)
{
    if(p>tot) return;
    if(check()) ans=(ans+1)%Mod;
    for(int i=p+1;i<=tot;++i)
    {
        se.insert(num[i]);
        Dfs3(i);
        se.erase(num[i]);  
    }
}
inline void swap(int &m,int &n)
{
    int tmp=n;
    n=m;
    m=tmp;
}
int main(int argc,char *argv[])
{
    freopen("cut.in","r",stdin);
    freopen("cut.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(int u,v,i=1;i<n;++i)
    {
        scanf("%d%d",&u,&v);
        if(u>v) swap(u,v);
        nextt[++cnt]=head[u];to[cnt]=v;head[u]=cnt;id[cnt]=i;
        nextt[++cnt]=head[v];to[cnt]=u;head[v]=cnt;id[cnt]=i;
        e[i]=(node){u,v};
    }
    Dfs1(1,0);
    memset(fw,0,sizeof(fw));
    Dfs2(1,0);
    Dfs3(0);
    printf("%d\n",ans);
    fclose(stdin); fclose(stdout);
    return 0;
}

#include<cstdio>
#include<cstdlib>
#define N 5555
#define M 786433
using namespace std;
typedef long long LL;
struct edge
{
    int t,n;
}e[N*2];
LL h[N],size[N],f[N][N],g[N],cnt[N];
int n,K,tote;
void add(int u,int v)
{
    e[++tote].t=v;
    e[tote].n=h[u];
    h[u]=tote;
    return ;
}
void dfs(int u,int fa)
{
    size[u]++; f[u][1]=1;
    for (int i=h[u];i;i=e[i].n)
    {
        int v=e[i].t;
        if (v==fa) continue;
        dfs(v,u);
        for (int j=1;j<=size[u]+size[v];j++) g[j]=0;
        for (int j=1;j<=size[u];j++) g[j]=cnt[v]*f[u][j]%M;
        for (int j=1;j<=size[u];j++)
        for (int k=1;k<=size[v];k++) g[j+k]=(g[j+k]+f[u][j]*f[v][k]%M)%M;
        for (int j=1;j<=size[u]+size[v];j++) f[u][j]=g[j];
        size[u]+=size[v];
    }
    for (int i=K;i<=size[u];i++) cnt[u]=(cnt[u]+f[u][i])%M;
    return ;
}
int main()
{
    freopen("cut.in","r",stdin);
    freopen("cut.out","w",stdout);
    scanf("%d %d",&n,&K);
    for (int i=1;i<n;i++)
    {
        int u,v;
        scanf("%d %d",&u,&v);
        add(u,v); add(v,u);
    }
    dfs(1,1);
    printf("%d\n",cnt[1]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}