2024/7/9 noip模拟鳃

T1

30pts
教训：存图双向边数组要开2倍（就是这么简单！）还害得我调了半个小时才发现，改后ac
code:

using namespace std;
int n,a,b,anode,bnode;
const int maxn = 1e6+10;
struct edge{
	int to,next;
}e[maxn];
int nodeflag = -1;
int head[maxn],siz[maxn],cnt,ans[maxn];
void addedge(int u,int v){
	cnt++;
	e[cnt].to = v;
	e[cnt].next = head[u];
	head[u] = cnt;
}
bool vis[maxn];
int dfs(int x,int fa){
	vis[x] = true;
	int size_ = 1;
	for(int i = head[x];i;i = e[i].next){
		if(!vis[e[i].to]) size_ += dfs(e[i].to,x);
	}
	if(size_ == a){
		anode = x;
		bnode = fa;
		nodeflag = 1;
	}
	if(size_ == b){
		anode = x;
		bnode = fa;
		nodeflag = 2;
	}
	return size_;
}
void dfs1(int x){
	vis[x] = true;
	ans[x] = a--;
	for(int i = head[x];i;i = e[i].next){
		if(!vis[e[i].to]) dfs1(e[i].to);
	}
}
void dfs2(int x){
	vis[x] = true;
	ans[x] = b--;
	ans[x] -= 2*ans[x];
	for(int i = head[x];i;i = e[i].next){
		if(!vis[e[i].to]) dfs2(e[i].to);
	}
}
int main(){
	cin>>n>>a>>b;
	int u,v;
	for(int i = 1;i < n;i++){
		cin>>u>>v;
		addedge(u,v);
		addedge(v,u);
	}
	dfs(v,u);
	if(anode == 0){
		cout<<"-1";
		return 0;
	}
	for(int i = 1;i <= n;i++) vis[i] = false;
	if(nodeflag == 1){
		vis[bnode] = true;
		dfs1(anode);
		dfs2(bnode);
	}
	else{
		vis[anode] = true;
		dfs1(bnode);
		dfs2(anode);
	}
	for(int i = 1;i <= n;i++) cout<<ans[i]<<" ";
}

T2


0pts 赛后思路理清

T3

赛中骗分 15pts 赛后ac。还有一种做法，贴边走一定是最优的，把所有矩形抽象成左线段，只取经过x轴的矩形，从左到右连边跑最短路。

T4 脑裂待解