# https://vjudge.net/contest/363991#problem/A

f[i]表示i结点往下走的最远距离，g[i]表示往上走的最远距离
f[i]=max(f[j])+i->v;
g[i]=max(g[pa],f[e[pa]->n]+e[pa]->v)+i->v;

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstring>
#define inf 2147483647
#define N 100010
#define p(a) putchar(a)
#define For(i,a,b) for(long long i=a;i<=b;++i)

using namespace std;
long long n,x,y;
long long d[N];
long long f[N],g[N];//f[]表示当前的节点到其叶子结点的最短距离，g[]表示这个点往上走的最大距离
struct node{
long long n;
long long v;
node *next;
}*e[N];

void in(long long &x){
long long y=1;char c=getchar();x=0;
while(c<'0'||c>'9'){if(c=='-')y=-1;c=getchar();}
while(c<='9'&&c>='0'){ x=(x<<1)+(x<<3)+c-'0';c=getchar();}
x*=y;
}
void o(long long x){
if(x<0){p('-');x=-x;}
if(x>9)o(x/10);
p(x%10+'0');
}

void clear(){
memset(f,0,sizeof(f));
memset(g,0,sizeof(g));
memset(e,0,sizeof(e));
}

void push(long long x,long long y,long long v){
node *p;
p=new node();
p->n=y;
p->v=v;
if(e[x]==0)
e[x]=p;
else{
p->next=e[x]->next;
e[x]->next=p;
}
}

long long dfs(long long x,long long fa){
for(node *i=e[x];i;i=i->next){
if(i->n!=fa)
f[x]=max(f[x],dfs(i->n,x)+i->v);
}
return f[x];
}

void bfs(long long x,long long fa,long long F){
long long temp=0;
for(node *i=e[fa];i;i=i->next){
if(i->n!=F&&i->n!=x)
g[x]=max(g[x],f[i->n]+i->v);
else if(i->n==x)
temp=i->v;
}
if(fa!=F) g[x]=max(g[fa],g[x])+temp;
for(node *i=e[x];i;i=i->next){
if(i->n!=fa) bfs(i->n,x,fa);
}
}

signed main(){
while(cin>>n){
clear();
For(i,2,n){
in(x);in(y);
push(i,x,y);
push(x,i,y);
}
dfs(1,1);
bfs(1,0,0);
For(i,1,n) o(max(f[i],g[i])),p('\n');
}
return 0;
}

posted @ 2020-03-27 22:08  WeiAR  阅读(...)  评论(...编辑  收藏