BZOJ 2725: [Violet 6]故乡的梦 最短路+线段树

#include<cstdio>
#include<algorithm>

typedef long long ll;
const int len(200000),lem(200000);
const ll INF(0x7fffffffffffffff);
struct Node{int nd,nx,co;}bot[lem*2+10];int tot=1,first[len+10];
int flag[len+10],last[len+10],tmp[len+10],Fr[len+10],To[len+10];
ll dis[len+10],Go[len+10],Bk[len+10],ans[len+10];
struct Data{int num;ll dis;}h[lem*2+10];int top;
struct ABC{int a,b,pos;ll c;}Edge[lem*2+10];
int n,m,x,y,c,S,T,Q;

ll min(ll a,ll b){return a>b?b:a;}
bool cmp(Data A,Data B){return A.dis>B.dis;}
bool cmp2(ABC A,ABC B){return Go[A.a]<Go[B.a];}
void swap(int &a,int &b){if(a==b)return;a^=b;b^=a;a^=b;}
void add(int a,int b,int c){bot[++tot]=(Node){b,first[a],c};first[a]=tot;}
template <class T>void read(T &x)
{
    x=0;int f=0;char c=getchar();
    while((c<‘0‘||c>‘9‘)&&c!=‘-‘)c=getchar(); if(c==‘-‘)f=1,c=getchar();
    while(c>=‘0‘&&c<=‘9‘){x=x*10+c-‘0‘;c=getchar();}
    x=f?-x:x;
}
struct MAP
{
    ll axle[len*2+10]; int up;
    void ins(ll x){axle[++up]=x;}
    void deal()
    {
        std::sort(axle+1,axle+1+up);
        int _up=1;//偷懒专用变量命名 
        for(int i=2;i<=up;i++)if(axle[i]!=axle[i-1])axle[++_up]=axle[i];
        up=_up;
    }
    int two(ll x)
    {
        int num=up;
        for(int mid,l=1,r=up;l<=r;)(axle[mid=(l+r)>>1]<=x)?num=mid,l=mid+1:r=mid-1;
        return num;
    }
}Map;
struct SMT
{
    int nx[lem*2+10][2],K,stot; ll small[lem*2+10];
    void build(int &k,int L,int R)
    {
        k=++stot; small[k]=INF; 
        if(L==R)return; int MID=(L+R)>>1; 
        build(nx[k][0],L,MID),build(nx[k][1],MID+1,R);
    }
    void change(int k,int L,int R,int x,ll y)
    {
        small[k]=min(small[k],y);    if(L==R)return;    int MID=(L+R)>>1;
        (x<=MID)?change(nx[k][0],L,MID,x,y):change(nx[k][1],MID+1,R,x,y);
    }
    ll query(int k,int L,int R,int x)
    {
        if(L==x)return small[k]; int MID=(L+R)>>1;
        return (x>MID)?query(nx[k][1],MID+1,R,x):
        min(small[nx[k][1]],query(nx[k][0],L,MID,x));
    }
}tree;

int dfs(int x)
{
    if(tmp[x])return tmp[x]; if(flag[x])return x;
    tmp[last[x]]=dfs(last[x]);
    return tmp[last[x]];
}
void Dij(int s,int t,int ty)
{
    for(int i=1;i<=n;i++)dis[i]=INF; dis[s]=0;
    h[top=1]=(Data){s,0}; Data now;
    while(top)
    {
        now=h[1],std::pop_heap(h+1,h+1+top,cmp),top--;
        while(dis[now.num]!=now.dis&&top)now=h[1],std::pop_heap(h+1,h+1+top,cmp),top--;
        if(dis[now.num]!=now.dis&&!top)break;
        for(int v=first[now.num];v;v=bot[v].nx)
        if(dis[bot[v].nd]>now.dis+bot[v].co)
        {
            dis[bot[v].nd]=now.dis+bot[v].co;
            last[bot[v].nd]=now.num;
            h[++top]=(Data){bot[v].nd,dis[bot[v].nd]};
            std::push_heap(h+1,h+1+top,cmp);
        }
    }
    if(ty==0)
        for(int v=t;v;v=last[v])flag[v]=1;
    if(ty==1)
        for(int i=1;i<=n;i++)
        if(dis[i]!=INF)tmp[i]=dfs(i);//O(n)
}//O(mlogm)
void Get()
{
    int x=S,Ei=2;
    while(x!=T)
    {
        if(!flag[x])break;flag[x]=0;
        for(int v=first[x];v;v=bot[v].nx)
        if(flag[bot[v].nd]&&Go[x]+bot[v].co==Go[bot[v].nd])
        {
            while(Go[Edge[Ei].a]<=Go[x]&&Ei<=tot)
            {
                if((Edge[Ei].pos^1)!=v&&Edge[Ei].pos!=v&&(Edge[Ei].pos^1)!=Edge[Ei-1].pos)
                tree.change(tree.K,1,Map.up,Map.two(Go[Edge[Ei].b]),Edge[Ei].c);
                Ei++;
            }
            ans[bot[v].nd]=tree.query(tree.K,1,Map.up,Map.two(Go[bot[v].nd]));
            if(ans[bot[v].nd]==INF)ans[bot[v].nd]=-1;
            last[bot[v].nd]=x;     x=bot[v].nd;
            break;
        }
    }
}//O(m+nlogn)
int main()
{
//    freopen("C.in","r",stdin);
//    freopen("C.out","w",stdout);
    read(n);read(m);
    for(int i=1;i<=m;i++)
    {
        read(x),read(y),read(c);
        add(x,y,c),add(y,x,c);
    }
    read(S),read(T);
    Dij(S,T,0);flag[0]=1;
    if(dis[T]!=INF)Dij(S,T,1);for(int i=1;i<=n;i++)Fr[i]=tmp[i],Go[i]=dis[i],tmp[i]=0;
    if(dis[T]!=INF)Dij(T,S,1);for(int i=1;i<=n;i++)To[i]=tmp[i],Bk[i]=dis[i],tmp[i]=0;
    for(int i=1;i<=n;i++)
        for(int v=first[i];v;v=bot[v].nx)
        {
            Edge[v]=(ABC){i,bot[v].nd,v,0};
            if(Go[Edge[v].a]>Go[Edge[v].b])swap(Edge[v].a,Edge[v].b);
//            if(Go[Edge[v].a]!=INF&&Bk[Edge[v].b]!=INF)
            Edge[v].c=Go[Edge[v].a]+Bk[Edge[v].b]+bot[v].co;
            Edge[v].a=Fr[i]; Edge[v].b=To[bot[v].nd];
            if(Go[Edge[v].a]>Go[Edge[v].b])swap(Edge[v].a,Edge[v].b);
//            else Edge[v].c=INF;
        }
    std::sort(Edge+2,Edge+1+tot,cmp2);
    for(int i=1;i<=n;i++)Map.ins(Go[i]); Map.deal();
    tree.build(tree.K,1,Map.up);
    for(int i=1;i<=n;i++)last[i]=0;
    Get();
    if(Go[T]==INF)Go[T]=-1;
    read(Q);
    for(int i=1;i<=Q;i++)
    {
        read(x),read(y);
        if(last[x]==y)swap(x,y);
        ll sum=(last[y]==x)?ans[y]:Go[T];
        if(sum==-1)printf("Infinity\n");else printf("%lld\n",sum);
    }
    return 0;
}