67 lines
1.6 KiB
C++
67 lines
1.6 KiB
C++
#include <iostream>
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#include <cstdio>
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using namespace std;
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const int inf=30000000;
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const int maxx=10003;
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struct Tree{
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int v,we,next;
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};
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Tree tree[maxx*2];
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int head[maxx*2],pt;
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int dp_f[maxx],dp_s[maxx];
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void adde(int x,int y,int we){
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tree[pt].v=y;
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tree[pt].we=we;
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tree[pt].next=head[x];
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head[x]=pt++;
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}
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int min(int a,int b){
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return a<b?a:b;
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}
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void dfs(int root,int pre){
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bool mark=false;
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for(int i=head[root];i;i=tree[i].next){
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int v=tree[i].v;
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if(pre==v)continue;
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mark=true;
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dfs(v,root);
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if(dp_f[root]>(dp_f[v]+tree[i].we)){
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dp_s[root]=dp_f[root];
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dp_f[root]=dp_f[v]+tree[i].we;
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}else if(dp_f[root]==dp_f[v]+tree[i].we){
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dp_s[root]=dp_f[root];
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}else{
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dp_s[root]=min(dp_s[root],dp_f[v]+tree[i].we);
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}
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}
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if(!mark)dp_f[root]=dp_s[root]=0;
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}
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int main(){
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int n;
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while(scanf("%d",&n)&&n){
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pt=1;
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int i,x,y,we,cnt;
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cnt=0;
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for(i=1;i<=n;i++){
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dp_f[i]=dp_s[i]=inf;
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}
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memset(head,0,sizeof(head));
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memset(tree,0,sizeof(tree));
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for(i=2;i<=n;i++){
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scanf("%d%d%d",&x,&y,&we);
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adde(x,y,we);
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adde(y,x,we);
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if(x==1 || y==1)cnt++;
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}
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dfs(1,0);
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int ans=1<<30;
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for(i=1;i<=n;i++){
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if(dp_f[i]==0 || dp_s[i]==0 ||dp_f[i]>20000000 ||dp_s[i]>20000000)continue;
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ans=min(ans,dp_f[i]+dp_s[i]);
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}
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if(cnt==1)ans=min(ans,dp_f[1]);
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printf("%d\n",ans);
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}
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return 0;
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}
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