视频链接:
P3574 [POI2014] FAR-FarmCraft - 洛谷 | 计算机科学教育新生态 (luogu.com.cn)
// 树形DP+贪心 O(nlogn) #include <iostream> #include <cstring> #include <algorithm> using namespace std; const int N=500005; int head[N],to[N<<1],ne[N<<1],idx; void add(int x,int y){ to[++idx]=y,ne[idx]=head[x],head[x]=idx; } int n,a[N],f[N],s[N],p[N]; bool cmp(int x,int y){ return f[x]-s[x]>f[y]-s[y]; } void dfs(int x,int fa){ f[x]=a[x]; for(int i=head[x];i;i=ne[i]) if(to[i]!=fa) dfs(to[i],x); int t=0; for(int i=head[x];i;i=ne[i]) if(to[i]!=fa) p[++t]=to[i]; sort(p+1,p+t+1,cmp); for(int i=1;i<=t;++i){ f[x]=max(f[x],s[x]+1+f[p[i]]); s[x]+=s[p[i]]+2; } } int main(){ scanf("%d",&n); for(int i=1;i<=n;++i) scanf("%d",&a[i]); for(int i=1,x,y;i<n;++i) scanf("%d%d",&x,&y), add(x,y),add(y,x); dfs(1,0); printf("%d\n",max(f[1],s[1]+a[1])); }
标签:head,fa,FAR,POI2014,int,FarmCraft,DP From: https://www.cnblogs.com/dx123/p/18423562