P1099 树网的核

来源：互联网发布：杭州市大数据管理局编辑：程序博客网时间：2024/06/06 13:14

这个代码写得令人作呕，请看我的另一篇博客，是在BZOJ上做的：http://blog.csdn.net/wamach/article/details/73195117

那还挂这个代码干嘛呢？显得洛谷的数据够差。

#pr\agma G\CC op\timize("O\2")#include<cstdio>#include<iostream>#include<algorithm>#include<cstring>#include<cstdlib>using namespace std;#define rep(i,j,k) for(i=j;i<=k;++i)#define per(i,j,k) for(i=j;i>=k;--i)#define ll long long#define db double#define mkp(x,y) make_pair(x,y)#define pii pair<int,int>#define X first#define Y secondconst int N=305;int n,s,Max[N<<1],pre[N],dep2[N],md,md2,ans;int he[N],ne[N<<1],to[N<<1],W[N<<1],tot,dep[N];void add(int x,int y,int z){to[++tot]=y;W[tot]=z;ne[tot]=he[x];he[x]=tot;}void DFS1(int x,int e){int i;dep[x]=dep[to[e]]+W[e];for(i=he[x];i;i=ne[i])if(i!=e){DFS1(to[i],i^1);if(e)Max[e^1]=max(Max[e^1],Max[i]+W[i]);}}void DFS2(int x,int e){int i,j;for(i=he[x];i;i=ne[i])if(i!=e){for(j=he[x];j;j=ne[j])if(j!=i&&j!=e)Max[i^1]=max(Max[i^1],W[j]+Max[j]);Max[i^1]=max(Max[i^1],W[e]+Max[e]);DFS2(to[i],i^1);}}void DFS(int x,int e){int i,j,y;dep2[x]=dep2[to[e]]+W[e];for(i=he[x];i;i=ne[i])if(i!=e){y=to[i];DFS(y,pre[y]=i^1);}}bool check(int x,int y){return y&&dep2[x]-dep2[y]<=s;}int main(){int i,j,x,y,z,tmp,h;ans=300001;scanf("%d%d",&n,&s);tot=1;rep(i,2,n){scanf("%d%d%d",&x,&y,&z);add(x,y,z),add(y,x,z);}DFS1(1,0);DFS2(1,0);rep(i,1,n)md=max(md,dep[i]);rep(i,1,n)if(md==dep[i]){memset(dep2,0,sizeof dep2);md2=0;memset(pre,0,sizeof pre);if(i==23)i=23;DFS(i,0);rep(j,1,n)md2=max(md2,dep2[j]);rep(j,1,n)if(dep2[j]==md2){for(x=j;;x=to[pre[x]]){for(tmp=0,h=he[x];h;h=ne[h])if(h!=pre[x])tmp=max(tmp,Max[h]+W[h]);ans=min(ans,max(Max[pre[x]]+W[pre[x]],tmp));if(x==i)break;for(y=x;check(x,z=to[pre[y]]);y=z){for(h=he[z];h;h=ne[h])if(h!=pre[z]&&to[h]!=y)tmp=max(tmp,Max[h]+W[h]);}tmp=max(tmp,Max[pre[y]]+W[pre[y]]);ans=min(ans,tmp);}}}printf("%d\n",ans);return 0;}

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