Submission #931851

#	Time	Username	Problem	Language	Result	Execution time	Memory
931851		Xiaoyang	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	252 ms	68212 KiB

Main

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
 
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl
#define pq priority_queue
#define inf 1ll<<60
#define rep(i,a,b) for (ll i=a;i<(b);i++)
#define MP make_pair
#define SZ(x) (int(x.size()))
#define mod 1000000007
#define ALL(x) x.begin(),x.end()
#define endl "\n"
void inc(ll &a,ll b) {a=(a+b)%mod;}
void dec(ll &a,ll b) {a=(a-b+mod)%mod;}
int prod(ll a,ll b) {return ll(a)*ll(b)%mod;}
int lowbit(ll x) {return x&(-x);}
ll p0w(ll base,ll p) {ll ret=1;while(p>0){if (p%2ll==1ll) ret=ret*base%mod;base=base*base%mod;p/=2ll;}return ret;}

const ll maxn=222222;
ll ht[maxn],dep[maxn],up[20][maxn],sz[maxn],fa[maxn];
ll dp[maxn];
vector<ll>alist[maxn];

//dp i is the max distance that cat moves at pillar with height i
void init(){
	rep(i,0,maxn)sz[i]=1,fa[i]=i;
}

ll findset(ll u){
	if(fa[u]==u)return u;
	return fa[u]=findset(fa[u]);
}

bool mergeset(ll u,ll v){
	u=findset(u);
	v=findset(v);
	if(u!=v){
		if(sz[u]<sz[v])swap(u,v);
		fa[v]=u;
		sz[u]+=sz[v];
	}
	
}

void dfs(ll u,ll p){
	up[0][u]=p;
	for(auto x:alist[u]){
		if(x==p)continue;
		dep[x]=dep[u]+1;
		dfs(x,u);
	}
}

ll lca(ll a,ll b){
	if(dep[a]<dep[b])swap(a,b);
	ll k=dep[a]-dep[b];
	rep(i,0,20){
		if((1ll<<i)&k)a=up[i][a];
	}
	if(a==b)return a;
	for(ll i=19;i>=0;i--){
		if(up[i][a]!=up[i][b]){
			a=up[i][a];
			b=up[i][b];
		}
	}
	return up[0][a];
}
ll dis(ll a,ll b){
	return dep[a]+dep[b]-2*dep[lca(a,b)];
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	//freopen("i.txt","r",stdin);
	ll n;cin>>n;
	rep(i,1,n+1)cin>>ht[i];
	rep(i,1,n){
		ll a,b;cin>>a>>b;
		alist[ht[a]].pb(ht[b]);
		alist[ht[b]].pb(ht[a]);
	}
	init();
	memset(up,-1,sizeof up);
	dfs(1,-1);
	rep(k,1,20){
		rep(i,1,n+1){
			if(up[k-1][i]!=-1){
				up[k][i]=up[k-1][up[k-1][i]];
			}
		}
	}
	rep(i,1,n+1){//iterate all the p values
		for(auto x:alist[i]){
			x=findset(x);
			if(x<i){
				fa[x]=i;
				dp[i]=max(dp[i],dp[x]+dis(i,x));
			}
		}
	}
	cout<<dp[n];
	return 0;
}

Compilation message (stderr)

Main.cpp: In function 'bool mergeset(ll, ll)':
Main.cpp:50:1: warning: no return statement in function returning non-void [-Wreturn-type]
   50 | }
      | ^

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26