BZOJ 4070: [Apio2015]雅加达的摩天楼 根号分治+spfa

此题卡Dijkstra...

Code:

#include <bits/stdc++.h>
#define N 30005
#define M 4000000
#define ll long long
#define inf 100000000
#define E 14300000
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
ll d[M];
int n,m,block,cnt,edges,s,t;
int id[N][103],hd[M],to[E],nex[E],val[E],done[M];
struct Node
{
    int u;
    ll dis;
    Node(int u=0,ll dis=0):u(u),dis(dis){}
    bool operator<(Node b) const
    {
        return b.dis<dis;
    }
};
priority_queue<Node>q;
void add(int u,int v,int c)
{
    // ++edges;
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=c;
}
void Dijkstra()
{
    memset(d,0x3f,sizeof(d));
    for(d[s]=0,q.push(Node(s,0));!q.empty();)
    {
        Node e=q.top(); q.pop();
        int u=e.u;
        if(done[u]) continue;
        done[u]=1;
        for(int i=hd[u];i;i=nex[i])
        {
            int v=to[i];
            if(d[v]>d[u]+val[i])
            {
                d[v]=d[u]+val[i];
                q.push(Node(v, d[v]));
            }
        }
    }
}
int main()
{
    int i,j,k;
    // setIO("input");
    scanf("%d%d",&n,&m);
    block=min(100,(int)sqrt(n));
    cnt = n + 23;
    for(i=1;i<=block;++i)
    {
        for(j=0;j<i;++j)
        {
            for(k=j;k<n;k+=i)
            {
                id[k][i]=++cnt;
                add(cnt,k,0);
                if(k>=i)
                    add(cnt-1,cnt,1), add(cnt,cnt-1,1);
            }
        }
    }
    for(i=1;i<=m;++i)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        if(i==1) s=a;
        if(i==2) t=a;
        if(b<=block)
            add(a, id[a][b], 0);
        else
        {
            int tt=0;
            for(j=a-b;j>=0;j-=b) add(a,j,++tt);
            tt=0;
            for(j=a+b;j<n;j+=b) add(a,j,++tt);
        }
    }
    // printf("%d %d\n",cnt,edges);
    Dijkstra();
    printf("%lld\n",d[t]>=inf?-1:d[t]);
    return 0;
}