제출 #432629

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
432629		juggernaut	Islands (IOI08_islands)	C++17	12 / 100	2071 ms	131076 KiB

islands

#include<bits/stdc++.h>
#define fr first
#define sc second
using namespace std;
void usaco(string s){freopen((s+".in").c_str(),"r",stdin);freopen((s+".out").c_str(),"w",stdout);}
typedef long long ll;
#define USING_ORDERED_SET 0
#if USING_ORDERED_SET
#include<bits/extc++.h>
using namespace __gnu_pbds;
template<class T>using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
#endif
template<class T>void umax(T &a,T b){if(a<b)a=b;}
template<class T>void umin(T &a,T b){if(b<a)a=b;}
#ifdef IOI2021SG
    #define printl(args...)printf(args)
#else
    #define printl(args...)((void)0)
#endif
const int N=1e6+5;
vector<pair<int,int>>g[N];
vector<pair<int,int>>gr[N];
vector<pair<int,int>>g1[N];
vector<pair<int,int>>g2[N];
int n;
pair<int,int>a[N];
int tin[N];
int fup[N];
bool used[N];
int timer;
vector<pair<int,int>>bridges;
void bridge(int v,int p){
    used[v]=true;
    fup[v]=tin[v]=++timer;
    for(auto [to,w]:gr[v])if(to!=p)
        if(used[to])umin(fup[v],tin[to]);
        else{
            bridge(to,v);
            umin(fup[v],fup[to]);
            if(fup[to]>tin[v]&&a[v].fr!=to){
                bridges.emplace_back(v,to);
                bridges.emplace_back(to,v);
                g1[v].emplace_back(to,w);
                g1[to].emplace_back(v,w);
            }
        }
}
vector<int>container;
int weight[2*N];
void cycle(int v){
    used[v]=true;
    container.push_back(v);
    for(auto [to,w]:g2[v])if(!used[to])cycle(to);
}
ll mx_depth[N];
void depth(int v,int p=0){
    for(auto [to,w]:g1[v])if(to!=p){
        depth(to,v);
        umax(mx_depth[v],mx_depth[to]+1ll*w);
    }
}
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d%d",&a[i].fr,&a[i].sc);
        g[i].emplace_back(a[i].fr,a[i].sc);
        g[a[i].fr].emplace_back(i,a[i].sc);
        if(a[a[i].fr].fr!=i){
            gr[i].emplace_back(a[i].fr,a[i].sc);
            gr[a[i].fr].emplace_back(i,a[i].sc);
        }
    }
    for(int i=1;i<=n;i++)if(!used[i])bridge(i,i);
    sort(bridges.begin(),bridges.end());
    for(int i=1;i<=n;i++){
        if(!binary_search(bridges.begin(),bridges.end(),make_pair(i,a[i].fr))){
            g2[i].emplace_back(a[i].fr,a[i].sc);
            g2[a[i].fr].emplace_back(i,a[i].sc);
        }
        used[i]=0;
    }
    ll ans=0;
    for(int i=1;i<=n;i++)if(!used[i]){
        container.clear();
        cycle(i);
        if(container.size()>1){
            int sz=container.size();
            for(int i=0;i<sz;i++){
                container.push_back(container[i]);
                depth(container[i]);
            }
            sz<<=1;
            for(int i=0;i+1<sz;i++){
                if(a[container[i]].fr==container[i+1])weight[i]=a[container[i]].sc;
                else{
                    weight[i]=a[container[i+1]].sc;
                }
            }
            int csz=(sz>>1);
            ll mx=0;
            for(int i=0;i<sz;i++){
                ll tmp=0;
                for(int j=i+1;j<sz;j++){
                    if(j-i>=csz)continue;
                    tmp+=1ll*weight[j-1];
                    umax(mx,tmp+1ll*mx_depth[container[i]]+1ll*mx_depth[container[j]]);
                }
            }
            reverse(container.begin(),container.end());
            for(int i=0;i+1<sz;i++){
                if(a[container[i]].fr==container[i+1])weight[i]=a[container[i]].sc;
                else{
                    weight[i]=a[container[i+1]].sc;
                }
            }
            for(int i=0;i<sz;i++){
                ll tmp=0;
                for(int j=i+1;j<sz;j++){
                    if(j-i>=csz)continue;
                    tmp+=1ll*weight[j-1];
                    umax(mx,tmp+1ll*mx_depth[container[i]]+1ll*mx_depth[container[j]]);
                }
            }
            ans+=mx;
        }
    }
    printf("%lld",ans);
}

컴파일 시 표준 에러 (stderr) 메시지

islands.cpp: In function 'void bridge(int, int)':
islands.cpp:35:29: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   35 |     for(auto [to,w]:gr[v])if(to!=p)
      |                             ^
islands.cpp: In function 'void usaco(std::string)':
islands.cpp:5:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    5 | void usaco(string s){freopen((s+".in").c_str(),"r",stdin);freopen((s+".out").c_str(),"w",stdout);}
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
islands.cpp:5:66: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    5 | void usaco(string s){freopen((s+".in").c_str(),"r",stdin);freopen((s+".out").c_str(),"w",stdout);}
      |                                                           ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
islands.cpp: In function 'int main()':
islands.cpp:63:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   63 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
islands.cpp:65:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |         scanf("%d%d",&a[i].fr,&a[i].sc);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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