【TYVJ】1520 树的直径

【算法】树的直径

memset(a,0,sizeof(a))

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=;
struct edge{int from,v,w;}e[maxn*];
int tot,X,n,head,tail,q[maxn],d[maxn],first[maxn];
bool v[maxn];
void insert(int u,int v,int w)
{tot++;e[tot].v=v;e[tot].w=w;e[tot].from=first[u];first[u]=tot;}
void bfs(int s)
{
    X=;
    memset(d,,sizeof(d));
    memset(v,,sizeof(v));//数组，值，范围
    head=;tail=;q[]=s;v[s]=;
    while(head<=tail)
     {
         int u=q[head++];
         if(d[u]>d[X])X=u;
         for(int i=first[u];i;i=e[i].from)
          if(!v[e[i].v])
           {
               v[e[i].v]=;
               d[e[i].v]=d[u]+e[i].w;
               q[++tail]=e[i].v;
           }
     }
}
int main()
{
    scanf("%d",&n);
    for(int i=;i<n;i++)
     {
         int u,v,w;
         scanf("%d%d%d",&u,&v,&w);
         insert(u,v,w);
         insert(v,u,w);
     }
    bfs();
    bfs(X);
    printf("%d",d[X]);
    return ;
}