4016: [FJOI2014]最短路径树问题 点分治

首先dijkstra一下最短路径树，然后点分治。

每次对每个子树进行操作，f[i][0]表示深度为i时的最长路径，f[i][1]表示深度为i时当前最长路径的方案数，两个数组倒一倒~不要忘记清零。

qwq开始犯了sb错误居然水过了。。。

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<vector>
#define inf 2000000000
#define N 30005
using namespace std;
int n,m,K,cnt,ans1,ans2,root,sz,sum;
int fm
,head
,head_
,size
;
int deep
,dis
,q
,fa
;
struct node {int v,id;} heap[N<<2];
int next[N<<1],list[N<<1],key[N<<1];
int next_[N<<2],list_[N<<2],key_[N<<2];
int f
[2],g
[2];
bool vis
;
vector <pair<int,int> > a
;
inline int read()
{
int a=0,f=1; char c=getchar();
while (c<'0'||c>'9') {if (c=='-') f=-1; c=getchar();}
while (c>='0'&&c<='9') {a=a*10+c-'0'; c=getchar();}
return a*f;
}
inline void insert(int x,int y,int z)
{
next[++cnt]=head[x];
head[x]=cnt;
list[cnt]=y;
key[cnt]=z;
}
inline void insert_(int x,int y,int z)
{
next_[++cnt]=head_[x];
head_[x]=cnt;
list_[cnt]=y;
key_[cnt]=z;
}
inline void push(node x)
{
heap[++sz]=x;
int now=sz;
while (now&&heap[now].v<heap[now>>1].v)
{
swap(heap[now],heap[now>>1]);
now>>=1;
}
}
inline void pop()
{
heap[1]=heap[sz--];
int now=1;
while (now<=(sz>>1))
{
int next=now<<1;
if (next<sz&&heap[next].v>heap[next+1].v) next++;
if (heap[now].v<heap[next].v) return;
swap(heap[now],heap[next]);
now=next;
}
}
inline void dijkstra()
{
for (int i=1;i<=n;i++) dis[i]=inf,vis[i]=0;
dis[1]=0;
push((node){0,1});
while (sz)
{
int x=heap[1].id; pop();
if (vis[x]) continue; vis[x]=1;
for (int i=head_[x];i;i=next_[i])
if (dis[list_[i]]>dis[x]+key_[i])
{
dis[list_[i]]=dis[x]+key_[i];
push((node){dis[list_[i]],list_[i]});
}
}
}
void dfs(int x)
{
vis[x]=1;
for (int i=head_[x];i;i=next_[i])
if (!vis[list_[i]]&&dis[list_[i]]==dis[x]+key_[i])
{
insert(x,list_[i],key_[i]);
insert(list_[i],x,key_[i]);
dfs(list_[i]);
}
}
void getroot(int x)
{
size[x]=1; fm[x]=0;
for (int i=head[x];i;i=next[i])
if (list[i]!=fa[x]&&!vis[list[i]])
{
fa[list[i]]=x;
getroot(list[i]);
size[x]+=size[list[i]];
fm[x]=max(fm[x],size[list[i]]);
}
fm[x]=max(fm[x],sum-size[x]);
if (fm[x]<fm[root]) root=x;
}
/*void getdeep(int x,int fa,int deep,int dis)
{
if (deep>K) return;
if (dis>g[deep][0]) g[deep][0]=dis,g[deep][1]=1;
else if (dis==g[deep][0]) g[deep][1]++;
for (int i=head[x];i;i=next[i])
if (list[i]!=fa&&!vis[list[i]])
getdeep(list[i],x,deep+1,dis+key[i]);
}*/
void work(int x,int nowsum)
{
vis[x]=1; f[0][1]=1;
for (int i=head[x];i;i=next[i])
if (!vis[list[i]])
{
//          getdeep(list[i],-1,1,key[i]);
int t=0,w=1;
q[1]=list[i];
deep[list[i]]=1; fa[list[i]]=x; dis[list[i]]=key[i];
while (t!=w)
{
int xx=q[++t];
int k=deep[xx];
if (k>K) break;
if (dis[xx]>g[k][0]) g[k][0]=dis[xx],g[k][1]=0;
if (dis[xx]==g[k][0]) g[k][1]++;
for (int j=head[xx];j;j=next[j])
if (!vis[list[j]]&&list[j]!=fa[xx])
{
fa[list[j]]=xx;
deep[list[j]]=deep[xx]+1;
dis[list[j]]=dis[xx]+key[j];
q[++w]=list[j];
}
}
for (int j=1;j<=K;j++)
{
if (g[j][0]+f[K-j][0]>ans1) ans1=g[j][0]+f[K-j][0],ans2=0;
if (g[j][0]+f[K-j][0]==ans1) ans2+=g[j][1]*f[K-j][1];
}
for (int j=1;j<=K;j++)
{
if (g[j][0]>f[j][0]) f[j][0]=g[j][0],f[j][1]=0;
if (g[j][0]==f[j][0]) f[j][1]+=g[j][1];
g[j][0]=g[j][1]=0;
}
}
for (int i=0;i<=K;i++) f[i][0]=f[i][1]=0;
for (int i=head[x];i;i=next[i])
if (!vis[list[i]])
{
sum=size[list[i]];
if (size[list[i]]>size[x]) size[list[i]]=nowsum-size[x];
root=0;
if (sum>=K) getroot(list[i]);
work(root,size[list[i]]);
}
}
int main()
{
n=read(); m=read(); K=read()-1;
for (int i=1;i<=m;i++)
{
int u=read(),v=read(),w=read();
a[u].push_back(make_pair(v,w));
a[v].push_back(make_pair(u,w));
}
for (int i=1;i<=n;i++)
{
sort(a[i].begin(),a[i].end());
for (int j=a[i].size()-1;~j;j--)
insert_(i,a[i][j].first,a[i][j].second);
}
dijkstra();
memset(vis,0,sizeof(vis));
cnt=0;
dfs(1);
root=0; fm[root]=inf; sum=n;
memset(vis,0,sizeof(vis));
getroot(1);
work(root,sum);
printf("%d %d\n",ans1,ans2);
return 0;
}