mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
67 lines
1.6 KiB
C++
67 lines
1.6 KiB
C++
|
#include <iostream>
|
||
|
|
#include <cstdio>
|
||
|
|
using namespace std;
|
||
|
|
const int inf=30000000;
|
||
|
|
const int maxx=10003;
|
||
|
|
struct Tree{
|
||
|
|
int v,we,next;
|
||
|
|
};
|
||
|
|
Tree tree[maxx*2];
|
||
|
|
int head[maxx*2],pt;
|
||
|
|
int dp_f[maxx],dp_s[maxx];
|
||
|
|
void adde(int x,int y,int we){
|
||
|
|
tree[pt].v=y;
|
||
|
|
tree[pt].we=we;
|
||
|
|
tree[pt].next=head[x];
|
||
|
|
head[x]=pt++;
|
||
|
|
}
|
||
|
|
int min(int a,int b){
|
||
|
|
return a<b?a:b;
|
||
|
|
}
|
||
|
|
void dfs(int root,int pre){
|
||
|
|
bool mark=false;
|
||
|
|
for(int i=head[root];i;i=tree[i].next){
|
||
|
|
int v=tree[i].v;
|
||
|
|
if(pre==v)continue;
|
||
|
|
mark=true;
|
||
|
|
dfs(v,root);
|
||
|
|
if(dp_f[root]>(dp_f[v]+tree[i].we)){
|
||
|
|
dp_s[root]=dp_f[root];
|
||
|
|
dp_f[root]=dp_f[v]+tree[i].we;
|
||
|
|
}else if(dp_f[root]==dp_f[v]+tree[i].we){
|
||
|
|
dp_s[root]=dp_f[root];
|
||
|
|
}else{
|
||
|
|
dp_s[root]=min(dp_s[root],dp_f[v]+tree[i].we);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
if(!mark)dp_f[root]=dp_s[root]=0;
|
||
|
|
}
|
||
|
|
int main(){
|
||
|
|
int n;
|
||
|
|
while(scanf("%d",&n)&&n){
|
||
|
|
pt=1;
|
||
|
|
int i,x,y,we,cnt;
|
||
|
|
cnt=0;
|
||
|
|
for(i=1;i<=n;i++){
|
||
|
|
dp_f[i]=dp_s[i]=inf;
|
||
|
|
}
|
||
|
|
memset(head,0,sizeof(head));
|
||
|
|
memset(tree,0,sizeof(tree));
|
||
|
|
for(i=2;i<=n;i++){
|
||
|
|
scanf("%d%d%d",&x,&y,&we);
|
||
|
|
adde(x,y,we);
|
||
|
|
adde(y,x,we);
|
||
|
|
if(x==1 || y==1)cnt++;
|
||
|
|
}
|
||
|
|
dfs(1,0);
|
||
|
|
int ans=1<<30;
|
||
|
|
for(i=1;i<=n;i++){
|
||
|
|
if(dp_f[i]==0 || dp_s[i]==0 ||dp_f[i]>20000000 ||dp_s[i]>20000000)continue;
|
||
|
|
ans=min(ans,dp_f[i]+dp_s[i]);
|
||
|
|
}
|
||
|
|
if(cnt==1)ans=min(ans,dp_f[1]);
|
||
|
|
printf("%d\n",ans);
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|