BZOJ 1576[Usaco2009 Jan]安全路经Travel

Solution:最短路树+并查集/树链剖分维护

#include <cstdio>
#include <queue>
#include <algorithm>
inline void swap(int &a,int &b)
{
    register int tmp=b;
    b=a;a=tmp;
}
inline int read()
{
    register int k=0,c=getchar(),f=1;
    while (c<'0'||c>'9')c=='-'&&(f=-1),c=getchar();
    while (c>='0'&&c<='9')k=k*10+c-'0',c=getchar();
    return k*f;
}
const int maxn=500000+100,inf=1<<30;
struct edg{
    int x,too,del,nxt;
}edge[maxn];
struct qaq{
    int dis,pos;
};
struct mc{
    int a,b,len;
}e[maxn];
bool v[maxn],used[maxn];
int vis[maxn];
int n,m,tot,tot2,a,b,c,dist[maxn],last[maxn],h[maxn];
int fq[maxn],eg[maxn],fa[maxn];
std::priority_queue<qaq>q;
bool operator<(qaq a,qaq b){return a.dis>b.dis;}
inline void add(int a,int b,int c)
{
    edge[++tot].nxt=last[a];
    last[a]=tot;
    edge[tot].too=b;
    edge[tot].x=a;
    edge[tot].del=c;
}
inline bool cmp(mc a,mc b)
{
    return a.len<b.len;
}
int gf(int now)
{
    return fa[now]==now?now:fa[now]=gf(fa[now]); 
}
inline void spfa()
{
    for (register int i=1;i<=n;i++)dist[i]=inf;
    v[1]=1;dist[1]=0;q.push((qaq){0,1});
    while (!q.empty())
    {
        register int now=q.top().pos;q.pop();
        for (register int i=last[now];i;i=edge[i].nxt)
        {
            if (dist[edge[i].too]>edge[i].del+dist[now])
            {
                dist[edge[i].too]=dist[now]+edge[i].del;
                fq[edge[i].too]=now;
                eg[edge[i].too]=i;
                if (!v[edge[i].too])
                {
                    v[edge[i].too]=1;
                    q.push((qaq){dist[edge[i].too],edge[i].too});
                }
            }
        }
        v[now]=0;
    }
}
int main()
{
    tot=1;
    n=read();m=read();
    for (register int i=1;i<=n;i++)fa[i]=i;
    for (register int i=1;i<=m;i++)a=read(),b=read(),c=read(),add(a,b,c),add(b,a,c);
    spfa();
    for (register int i=1;i<=n;i++)used[eg[i]]=used[eg[i]^1]=1;
    for (register int i=1;i<=tot;i++)
    if (!used[i])
    {
        e[++tot2].a=edge[i].x;e[tot2].b=edge[i].too;
        e[tot2].len=edge[i].del+dist[edge[i].x]+dist[edge[i].too];
    }
    std::sort(e+1,e+tot2+1,cmp);
    for(register int i=1;i<=tot2;i++)
    {
        register int a=e[i].a,b=e[i].b,f1=gf(a),f2=gf(b),lasta=0,lastb=0;
        while (f1!=f2)
        {
            if (dist[a]<dist[b])swap(a,b),swap(f1,f2),swap(lasta,lastb);
            if (!vis[a])
            {
                vis[a]=i;
                if (lasta)fa[lasta]=a;
            }else if (lasta)fa[lasta]=f1;
            lasta=f1;a=fq[lasta];f1=gf(a);
        }
    }
    for (register int i=2;i<=n;i++)
    if (!vis[i])printf("-1
");else printf("%d
",e[vis[i]].len-dist[i]);
}