Submission #4621310

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Source Code Expand

#include<bits/stdc++.h>
#include<tr1/unordered_map>
#define CLR(a,x) memset(a,x,sizeof(a))
#define MP make_pair
#define fi first
#define se second
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pa;
const int maxn=1e5+10;

inline ll rd(){
    ll x=0;char c=getchar();int neg=1;
    while(c<'0'||c>'9'){if(c=='-') neg=-1;c=getchar();}
    while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
    return x*neg;
}

int N,eg[maxn*2][3],egh[maxn],ect;
int siz[maxn];
int aaa;
ll sum,n0,ans2,ans;

inline void adeg(int a,int b,int c){
	eg[++ect][0]=b,eg[ect][1]=egh[a],egh[a]=ect,eg[ect][2]=c;
}

inline void dfs(int x,int f,int ine){
	siz[x]=1;
	for(int i=egh[x];i;i=eg[i][1]){
		int b=eg[i][0];if(b==f) continue;
		dfs(b,x,i);siz[x]+=siz[b];
		n0+=eg[i][2]*(siz[b]>=N-siz[b]);
	}
	sum+=2ll*min(siz[x],N-siz[x])*eg[ine][2];
}

inline void dfs2(int x,int f,ll n){
	// printf("~%d %d %d\n",x,f,n);
	if(sum-n>ans&&n) ans=sum-n,aaa=x;
	for(int i=egh[x];i;i=eg[i][1]){
		int b=eg[i][0];if(b==f) continue;
		dfs2(b,x,n+eg[i][2]*((siz[b]<=N-siz[b])-(siz[b]>=N-siz[b])));
	}
}
inline void dfs3(int x,int f,ll n){
	if(x!=aaa) ans2=max(ans2,ans-n);
	for(int i=egh[x];i;i=eg[i][1]){
		int b=eg[i][0];if(b==f) continue;
		dfs3(b,x,n+eg[i][2]*((siz[b]<=N-siz[b])-(siz[b]>=N-siz[b])));
	}
}

int main(){
    //freopen("","r",stdin);
	N=rd();
	for(int i=1;i<N;i++){
		int a=rd(),b=rd(),c=rd();
		adeg(a,b,c),adeg(b,a,c);
	}
	dfs(1,0,0),dfs2(1,0,n0);
	// dfs3(1,0,n0);
	printf("%lld\n",ans);
    return 0;
}

Submission Info

Judge Result