제출 #302331

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
302331		Hemimor	Islands (IOI08_islands)	C++14	15 / 100	922 ms	131076 KiB

islands

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <numeric>
#include <cassert>
#include <vector>
#include <cmath>
#include <queue>
#include <set>
#include <map>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

const int M=1000000;
int n,deg[M],par[M];
bool vis[M];
vp g[M];
ll res,c[M],d[M];

ll dfs(int v,int pre=-1){
	vl a(2,0);
	for(auto p:g[v]){
		int u=p.first;
		if(!deg[u]&&u!=pre) a.push_back(dfs(u,v)+p.second);
	}
	sort(a.rbegin(),a.rend());
	res=max(res,a[0]+a[1]);
	return a[0];
}

ll f(int v){
	res=0;
	vi a,b;
	vis[v]=1;
	queue<int> q;
	q.push(v);
	while(!q.empty()){
		v=q.front();q.pop();
		a.push_back(v);
		for(auto p:g[v]){
			int u=p.first;
			if(!vis[u]){
				vis[u]=1;
				q.push(u);
			}
		}
	}
	for(auto i:a) if(deg[i]==1) q.push(i);
	while(!q.empty()){
		v=q.front();q.pop();
		deg[v]--;
		for(auto p:g[v]){
			int u=p.first;
			if(deg[u]){
				par[v]=u;
				deg[u]--;
				if(deg[u]==1) q.push(u);
			}
		}
	}
	int len=0;
	for(auto i:a) if(deg[i]){
		v=i;
		len++;
	}
	int now=v,pre=-1,pw=-1;
	ll t=0;
	do{
		b.push_back(now);
		c[now]=t;
		vp tmp;
		for(auto p:g[now]){
			int u=p.first;
			tmp.push_back(p);
			if(u!=pre){
				pre=now;
				pw=p.second;
				now=u;
				t+=p.second;
				break;
			}
		}
		if(len==2&&b.size()==2){
			if(tmp[0].second==pw) swap(tmp[0],tmp[1]);
			now=v;
			t+=tmp[0].second;
		}
	}while(now!=v);
	ll res=0,mx=-INF;
	for(auto i:b) d[i]=dfs(i);
	for(auto i:b){
		res=max(res,c[i]+d[i]+mx);
		mx=max(mx,-c[i]+d[i]);
	}
	mx=-INF;
	for(auto i:b){
		res=max(res,t-c[i]+d[i]+mx);
		mx=max(mx,c[i]+d[i]);
	}
	return res;
}

int main(){
	fill(par,par+M,-1);
	scanf("%d",&n);
	for(int u=0;u<n;u++){
		int v,w;
		scanf("%d%d",&v,&w);
		v--;
		g[u].push_back({v,w});
		g[v].push_back({u,w});
		deg[u]++,deg[v]++;
	}
	ll sum=0;
	for(int i=0;i<n;i++) if(!vis[i]) sum+=f(i);
	printf("%lld\n",sum);
}

컴파일 시 표준 에러 (stderr) 메시지

islands.cpp: In function 'int main()':
islands.cpp:129:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  129 |  scanf("%d",&n);
      |  ~~~~~^~~~~~~~~
islands.cpp:132:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  132 |   scanf("%d%d",&v,&w);
      |   ~~~~~^~~~~~~~~~~~~~

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