SGU 143.Long Live the Queen(女王万岁)
2018-01-21 22:25
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先确定一个根节点,然后dp[u]表示一定取u的联通块的最大点权和
dp[u]=1+∑dp[v](v是u的孩子并且dp[v]大于0)
代码:
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
using namespace std;
const int maxn=210000;
int head[maxn]={},next[maxn]={},to[maxn]={},w[maxn]={};
int dp[maxn]={};
int n,cnt,ans;
inline void add(int u,int v){
to[++cnt]=v;
next[cnt]=head[u];
head[u]=cnt;
}
void dfs(int u,int fa){
dp[u]=w[u];
for(int i=head[u];i!=-1;i=next[i])if(to[i]!=fa){
int v=to[i];
dfs(v,u);
if(dp[v]>0) dp[u]+=dp[v];
}
ans=max(ans,dp[u]);
}
int main()
{
while(scanf("%d",&n)==1){
memset(head,-1,sizeof(head));
memset(dp,0,sizeof(dp));
for(int i=1;i<=n;i++) scanf("%d",&w[i]);
cnt=0;ans=0;
for(int i=1;i<n;i++){
int u,v;
scanf("%d%d",&u,&v);
add(u,v);add(v,u);
}
dfs(1,-1);
printf("%d\n",ans);
}
return 0;
}
dp[u]=1+∑dp[v](v是u的孩子并且dp[v]大于0)
代码:
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
using namespace std;
const int maxn=210000;
int head[maxn]={},next[maxn]={},to[maxn]={},w[maxn]={};
int dp[maxn]={};
int n,cnt,ans;
inline void add(int u,int v){
to[++cnt]=v;
next[cnt]=head[u];
head[u]=cnt;
}
void dfs(int u,int fa){
dp[u]=w[u];
for(int i=head[u];i!=-1;i=next[i])if(to[i]!=fa){
int v=to[i];
dfs(v,u);
if(dp[v]>0) dp[u]+=dp[v];
}
ans=max(ans,dp[u]);
}
int main()
{
while(scanf("%d",&n)==1){
memset(head,-1,sizeof(head));
memset(dp,0,sizeof(dp));
for(int i=1;i<=n;i++) scanf("%d",&w[i]);
cnt=0;ans=0;
for(int i=1;i<n;i++){
int u,v;
scanf("%d%d",&u,&v);
add(u,v);add(v,u);
}
dfs(1,-1);
printf("%d\n",ans);
}
return 0;
}
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