BZOJ 3257: 树的难题

树形DP

#include
#include
#define rep(i,x,y) for (int i=x; i<=y; i++)
using namespace std;
int cnt,last[300005],c[300005];
long long F[300005][2][3],G[2][3];
struct node{
	int to,next,val;
}e[600005];
void add(int a,int b,int c){
	e[++cnt].to=b;
	e[cnt].next=last[a];
	e[cnt].val=c;
	last[a]=cnt;
}
void dfs(int x,int fa){
	rep(i,0,1) rep(j,0,2) F[x][i][j]=1ll<<60;
	F[x][c[x]==0][c[x]==1]=0;
	for (int i=last[x]; i; i=e[i].next){
		int V=e[i].to;
		if (V==fa) continue;
		dfs(V,x);
		rep(nowx,0,1) rep(nowy,0,2) G[nowx][nowy]=1ll<<60;
		rep(prex,0,1) rep(prey,0,2)
		rep(nowx,0,1) rep(nowy,0,2){
			int tox=min(1,prex+nowx),toy=min(2,prey+nowy);
			if (tox!=1 || toy!=2) G[tox][toy]=min(G[tox][toy],F[x][prex][prey]+F[V][nowx][nowy]);
			G[prex][prey]=min(G[prex][prey],F[x][prex][prey]+F[V][nowx][nowy]+e[i].val);
		}
		rep(nowx,0,1) rep(nowy,0,2) F[x][nowx][nowy]=G[nowx][nowy];
	}
}
int main(){
	int T;
	scanf("%d",&T);
	while (T--){
		int n;
		scanf("%d",&n);
		for (int i=1; i<=n; i++) scanf("%d",&c[i]);
		cnt=0;
		for (int i=1; i<=n; i++) last[i]=0;
		for (int i=1; i

　　

转载于:https://www.cnblogs.com/silenty/p/9858023.html