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# | Author | Problem | Lang | Verdict | Time | Memory | Sent | Judged | |
---|---|---|---|---|---|---|---|---|---|
132100655 |
Practice: Untitled37 |
835F - 34 | C++14 (GCC 6-32) | Accepted | 233 ms | 28484 KB | 2021-10-16 10:44:38 | 2021-10-16 10:44:38 |
#include<bits/stdc++.h> #define int long long using namespace std; const int N=200005,INF=1e18+5; struct edge{int to,wei,nxt;}e[N<<1]; int n,tot=0,cnt=0,ans1=0,ans2=INF,res,head[N],cir[N],vis[N],f[N],we[N],l[N],l0[N],r[N],r0[N]; inline void adde(int x,int y,int w) {e[++tot]=(edge){y,w,head[x]},head[x]=tot;}//加边 inline int fnd(int x,int fa=-1) { if(vis[x]) return x;else vis[x]=-1; for(int i=head[x];i;i=e[i].nxt) if(e[i].to!=fa) {res=fnd(e[i].to,x);if(res) return cir[++cnt]=x,we[cnt]=e[i].wei,vis[x]=1,res==x?0:res;} return 0; } inline void dfs(int x,int fa=-1) { for(int i=head[x];i;i=e[i].nxt) if(vis[e[i].to]!=1&&e[i].to!=fa) dfs(e[i].to,x),ans1=max(ans1,f[x]+f[e[i].to]+e[i].wei),f[x]=max(f[x],f[e[i].to]+e[i].wei); } signed main() { scanf("%lld",&n),memset(vis,0,sizeof(vis)),memset(f,0,sizeof(f)); for(int i=1,x,y,w;i<=n;i++) scanf("%lld%lld%lld",&x,&y,&w),adde(x,y,w),adde(y,x,w); fnd(1),we[0]=0;for(int i=1;i<=cnt;i++) dfs(cir[i]),we[i]+=we[i-1]; res=l[0]=l0[0]=-INF; for(int i=1;i<=cnt;i++) l0[i]=max(l0[i-1],f[cir[i]]+we[i]+res),l[i]=max(l[i-1],f[cir[i]]+we[i]),res=max(res,f[cir[i]]-we[i]); res=r[cnt+1]=r0[cnt+1]=-INF;//反着递推 for(int i=cnt;i>=1;i--) r0[i]=max(r0[i+1],f[cir[i]]-we[i]+res),r[i]=max(r[i+1],f[cir[i]]+we[cnt]-we[i]),res=max(res,f[cir[i]]+we[i]); for(int i=1;i<=cnt;i++) ans2=min(ans2,max(l[i-1]+r[i],max(l0[i-1],r0[i]))); return printf("%lld\n",max(ans1,ans2)),0; }
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