BZOJ3365路程統計

我是轉別人的……實在不想寫了

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define MAX 40005
#pragma comment(linker, "/STACK:1024000000,1024000000")   
#define rep(i,j,k) for(int i=j;i<=k;i++)

using namespace std;

int tot=0,ans=0;
int n,m,k,to[2*MAX],next[2*MAX],head[MAX],value[2*MAX];
int u[MAX],t,size[MAX],f[MAX],done[MAX];

struct wbysr
{
  int belong,dis;
}a[MAX];

bool cmp(wbysr a1,wbysr a2)
{
  return a1.dis<a2.dis;
}

void add(int from,int To,int weight)
{
  to[++tot]=To;
  next[tot]=head[from];
  value[tot]=weight;
  head[from]=tot;
}

void dfs(int x,int fa)
{
  u[++t]=x;
  size[x]=1;
  f[x]=0;
  for(int i=head[x];i;i=next[i])
    if(!done[to[i]]&&to[i]!=fa)
      dfs(to[i],x),size[x]+=size[to[i]],f[x]=max(f[x],size[to[i]]);
  return;
}

int find_root(int x)
{
  t=0;
  dfs(x,0);
  int Min=0x7fffffff,p;
  rep(i,1,t)
    if(max(size[x]-size[u[i]],f[u[i]])<=Min)
      Min=max(size[x]-size[u[i]],f[u[i]]),p=u[i];
  return p;
}

void dfs2(int x,int fa,int Belong,int dist)
{
  a[++t].belong=Belong;
  a[t].dis=dist;
  for(int i=head[x];i;i=next[i])
    if(!done[to[i]]&&to[i]!=fa)
      dfs2(to[i],x,Belong,dist+value[i]);
  return;
}

inline void calc(int x)
{
  t=0;
  a[++t].belong=x;
  a[t].dis=0;
  for(int i=head[x];i;i=next[i])
    if(!done[to[i]])
      dfs2(to[i],x,to[i],value[i]);
  sort(a+1,a+1+t,cmp);
  int r=t,same[MAX]={0};
  rep(i,1,t)
    same[a[i].belong]++;
  rep(l,1,t)
  {
    while(a[l].dis+a[r].dis>k&&r>l)
      same[a[r].belong]--,r--;
    same[a[l].belong]--;
    if(r>l)
      ans+=r-l-same[a[l].belong];
  }
}

inline void work(int x)
{
  int root=find_root(x);
  done[root]=1;
  calc(root);
//  printf("work %d %d %d\n",x,root,ans);
  for(int i=head[root];i;i=next[i])
    if(!done[to[i]])
      work(to[i]);
  return;
}

int main()
{
  scanf("%d%d",&n,&m);
  rep(i,1,m)
  {
    int a1,a2,a3;
    char ch;
    scanf("%d%d%d %c",&a1,&a2,&a3,&ch);
    add(a1,a2,a3);
    add(a2,a1,a3);
  }
  scanf("%d",&k);
  ans=0;
  work(1);
  printf("%d\n",ans);
  return 0;
}