xx
树的直径
1 #include<bits/stdc++.h> 2 using namespace std; 3 #define ll long long 4 struct re{ 5 ll v; 6 ll nex; 7 ll w; 8 }; 9 const ll N=1e6; 10 re edge[N*2]; 11 ll f[N],dist[N],tot,n; 12 ll maxer,maxv; 13 bool p[N]; 14 struct c1{ 15 ll a; 16 ll b; 17 ll w; 18 }; 19 c1 cun[N]; 20 void ad(ll x,ll y,ll d){ 21 tot++; 22 edge[tot].nex=f[x]; 23 edge[tot].v=y; 24 edge[tot].w=d; 25 f[x]=tot; 26 cun[tot].a=y; 27 cun[tot].b=x; 28 cun[tot].w=d; 29 } 30 void ad1(ll x,ll y,ll d){ 31 tot++; 32 edge[tot].nex=f[x]; 33 edge[tot].v=y; 34 edge[tot].w=d; 35 f[x]=tot; 36 } 37 ll loop,cnt[N],lp[N]; 38 void dfs1(ll x){ 39 cnt[x]++; 40 if(cnt[x]==2){loop=x;return;} 41 if(f[x]==-1)return; 42 dfs1(edge[f[x]].v); 43 } 44 void dfs2(ll x){ 45 if(x==loop&&cnt[x]==5)return; 46 cnt[x]=5; 47 tot++; 48 lp[tot]=x; 49 dfs2(edge[f[x]].v); 50 } 51 /*void spfa(ll x){ 52 maxer=0; 53 dist[x]=0; 54 // memset(p,0,sizeof(p));//关注多组数据的读入清空 55 p[x]=0; 56 queue<ll>s; 57 s.push(x); 58 while(s.empty!=1){ 59 ll az=s.front(); 60 ll k=f[az]; 61 s.pop(); 62 while(k!=-1){ 63 ll dot; 64 dot=edge[k].v; 65 if((dist[dot]<dist[az]+edge[k].w&&dist[dot]!=-1)||dist[dot]==-1){ 66 dist[dot]=dist[az]+edge[k].w; 67 if(!p[dot]){p[dot]=1;s.push(dot);} 68 if(dist[dot]>maxer){maxer=dist[dot];maxv=dot;} 69 } 70 k=edge[k].nex; 71 } 72 p[az]=0; 73 } 74 }*/ 75 int main(){ 76 memset(f,-1,sizeof(-1)); 77 cin>>n; 78 for(int i=1;i<=n;i++){ 79 ll it1,it2,it3; 80 cin>>it1>>it2>>it3; 81 ad(it1,it2,it3); 82 } 83 tot=n; 84 for(int i=1;i<=n;i++)ad1(cun[i].a,cun[i].b,cun[i].w); 85 return 0; 86 }
http://www.cnblogs.com/Khada-Jhin/p/9468144.html
https://blog.csdn.net/lvzelong2014/article/details/80647506?utm_source=blogxgwz4