【算法】树的直径

memset(a,0,sizeof(a))

#include
      
       #include
       
        #include
        
         using namespace std;const int maxn=10010;struct edge{
    int from,v,w;}e[maxn*2];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=0;    memset(d,0,sizeof(d));    memset(v,0,sizeof(v));//数组，值，范围     head=1;tail=1;q[1]=s;v[s]=1;    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]=1;               d[e[i].v]=d[u]+e[i].w;               q[++tail]=e[i].v;           }     }}int main(){    scanf("%d",&n);    for(int i=1;i