题解：ACM-ICPC 2018 南京赛区网络预赛

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An Olympian Math Problem

#include<stdio.h>
int main()
{
    long long t,n;
    for(scanf("%lld",&t); t--; printf("%lld\n",n-1))
        scanf("%lld",&n);
}

AC Challenge

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;

const int maxn=25;
const int maxv=1<<22;
const long long inf=-100000000000000;

queue <long long> q[2];
long long f[2][maxv];
bool inq[maxv];
int pre[maxn];
int val[maxn][maxn];
int n,a,b,s,u,V;
long long ans;

int main()
{
    scanf("%d",&n);
    for (int i=1;i<=n;i++)
    {
        scanf("%d%d",&a,&b);
        for (int j=1;j<=n;j++) val[i][j]=a*j+b;
        scanf("%d",&s);
        for (int j=1;j<=s;j++)
        {
            scanf("%d",&u);
            pre[i]+=1<<u;
        }
    }
    V=1<<n+1;
    for (int i=1;i<=n;i++)
     if (pre[i]==0) f[1][1<<i]=val[i][1],q[1].push(1<<i);
    for (int i=2;i<=n;i++)
    {
        memset(inq,false,sizeof(inq));
        while (!q[(i+1)%2].empty())
        {
            int g=q[(i+1)%2].front();
            //printf("%d %d\n",i,g);
            q[(i+1)%2].pop();
            for (int j=1;j<=n;j++)
            {
                if ((1<<j)&g) continue;
                if ((g&pre[j])!=pre[j]) continue;
            //  if (f[(i+1)%2][k]+val[j][i]>f[i%2][k+(1<<j)]) printf("%d %d %d\n",j,k,f[(i+1)%2][k]+val[j][i]);
                int nxt=g+(1<<j);
                if (f[(i+1)%2][g]+val[j][i]>f[i%2][nxt])
                {
                    f[i%2][nxt]=f[(i+1)%2][g]+val[j][i];    
                    if (!inq[nxt]) q[i%2].push(nxt),inq[nxt]=true;
                    ans=max(ans,f[i%2][nxt]);
                }
            }
            f[(i+1)%2][g]=inf;
        }
    }
    printf("%lld",ans);
    return 0;
}

Sum

线性筛处理一下。

#include<cstdio>
#include<vector>
using namespace std;
const int N=2e7+7;
struct EulerSieve
{
    vector<int> p,m,f;
    EulerSieve(int N):m(N,0),f(N)
    {
        f[1]=1;
        for(long long i=2,k; i<N; ++i)
        {
            if(!m[i])p.push_back(m[i]=i),f[i]=2;
            for(int j=0; j<p.size()&&(k=i*p[j])<N; ++j)
                if(f[k]=f[i]*2,(m[k]=p[j])==m[i])
                {
                    f[k]/=4;
                    break;
                }
        }
        for(int i=0,p3; p3=p[i]*p[i]*p[i],p3<N; ++i)
            for(int j=p3; j<N; j+=p3)
                f[j]=0;
    }
} e(N);
long long sum[N];
int t,n;
int main()
{
    for(int i=1; i<N; ++i)sum[i]=sum[i-1]+e.f[i];
    for(scanf("%d",&t); t--; printf("%lld\n",sum[n]))
        scanf("%d",&n);
}

Magical Girl Haze

居然有spfa过的…

#include<cstdio>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;
const ll INF=1e18;
const int N=12e5,NPOS=-1;
struct Edge
{
    int from,to;
    ll dist;
    int a;
} e[N<<2];
int va[N],es,vs;
void init(int n)
{
    fill(va,va+(vs=n),NPOS);
    es=0;
}
void add(const Edge &ed)
{
    e[es]=ed;
    e[es].a=va[ed.from];
    va[ed.from]=es++;
}
ll d[N];
void ask(int s)
{
    fill(d,d+vs,INF);
    priority_queue<pair<ll,int> > q;
    for(q.push(make_pair(d[s]=0,s)); !q.empty();)
    {
        ll dis=-q.top().first;
        int u=q.top().second;
        if(q.pop(),d[u]<dis)continue;
        for(int k=va[u],to; k!=NPOS; k=e[k].a)
            if(to=e[k].to,d[to]>d[u]+e[k].dist)
            {
                d[to]=d[u]+e[k].dist;
                q.push(make_pair(-d[to],to));
            }
    }
}
int main()
{
    int t,n,m,k;
    for(scanf("%d",&t); t--;)
    {
        scanf("%d%d%d",&n,&m,&k);
        init(n*(k+2));
        for(int i=0,u,v,c; i<m; ++i)
        {
            scanf("%d%d%d",&u,&v,&c),--u,--v;
            for(int j=0; j<=k; ++j)
                add({u+j*n,v+j*n,c}),add({u+j*n,v+(j+1)*n,0});
        }
        ask(0);
        printf("%lld\n",d[n*(k+1)-1]);
    }
}