제출 #586885

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
586885		Bench0310	Flood (IOI07_flood)	C++17	0 / 100	583 ms	45336 KiB

flood

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const int N=100001;
int tree[4*(N+5)];
int points[N][2];
array<int,3> hot_pos[4*N];

void update(int idx,int l,int r,int ql,int qr,int x)
{
    if(ql>qr) return;
    if(l==ql&&r==qr) tree[idx]=x;
    else
    {
        int m=(l+r)/2;
        update(2*idx,l,m,ql,min(qr,m),x);
        update(2*idx+1,m+1,r,max(ql,m+1),qr,x);
    }
}

int query(int idx,int l,int r,int pos)
{
    if(l==r) return tree[idx];
    int m=(l+r)/2;
    if(pos<=m) return max(tree[idx],query(2*idx,l,m,pos));
    else return max(tree[idx],query(2*idx+1,m+1,r,pos));
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    int hot_cnt=0;
    auto add_hot=[&](int x,int y)->int
    {
        hot_cnt++;
        hot_pos[hot_cnt]={x,y,hot_cnt};
        return hot_cnt;
    };
    vector<array<int,4>> point_hots(n+1);
    vector<array<int,2>> x_compress,y_compress;
    for(int i=1;i<=n;i++)
    {
        auto &[x,y]=points[i];
        cin >> x >> y;
        x_compress.push_back({x,i});
        y_compress.push_back({y,i});
    }
    sort(x_compress.begin(),x_compress.end());
    sort(y_compress.begin(),y_compress.end());
    int hx=0;
    int hy=0;
    for(int i=0;i<n;i++)
    {
        if(i>0&&x_compress[i][0]!=x_compress[i-1][0]) hx++;
        if(i>0&&y_compress[i][0]!=y_compress[i-1][0]) hy++;
        points[x_compress[i][1]][0]=hx;
        points[y_compress[i][1]][1]=hy;
    }
    for(int i=1;i<=n;i++)
    {
        auto &[x,y]=points[i];
        int t=0;
        for(int j=0;j<=1;j++) for(int k=0;k<=1;k++) point_hots[i][t++]=add_hot(x+j,y+k);
    }
    int m;
    cin >> m;
    vector<array<int,2>> walls(m+1,{0,0});
    vector<array<int,2>> wall_hots(m+1,{0,0});
    for(int i=1;i<=m;i++)
    {
        auto &[a,b]=walls[i];
        cin >> a >> b;
        if(points[a]>points[b]) swap(a,b);
        if(points[a][0]==points[b][0]) wall_hots[i]={point_hots[a][1],point_hots[a][3]};
        else wall_hots[i]={point_hots[a][2],point_hots[a][3]};
    }
    vector<array<int,2>> vedges;
    auto add_edge=[&](int a,int b)
    {
        vedges.push_back({a,b});
        vedges.push_back({b,a});
    };
    auto process=[&]()
    {
        //extract edges
        fill(tree,tree+4*(N+5),-1);
        vector<array<int,2>> prv(N+1,{-1,-1}); //x,hot_id
        vector<array<int,4>> events; //x,tp,[y,hot_id] or [yl,yr]
        for(int i=1;i<=hot_cnt;i++) events.push_back({hot_pos[i][0],0,hot_pos[i][1],i});
        for(int i=1;i<=m;i++)
        {
            auto [a,b]=walls[i];
            auto [xa,ya]=points[a];
            auto [xb,yb]=points[b];
            if(xa==xb) events.push_back({xa,1,ya+1,yb});
        }
        sort(events.begin(),events.end());
        for(auto [x,tp,yl,yr]:events)
        {
            if(tp==0)
            {
                int w=query(1,0,N,yl);
                auto [px,pid]=prv[yl];
                if(w<px) add_edge(yr,pid);
                prv[yl]={x,yr};
            }
            else update(1,0,N,yl,yr,x);
        }
        //flip coordinates
        for(int i=1;i<=n;i++) swap(points[i][0],points[i][1]);
        for(int i=1;i<=hot_cnt;i++) swap(hot_pos[i][0],hot_pos[i][1]);
    };
    process();
    process();
    vector<int> cc_id(hot_cnt+1,0);
    int cc_cnt=0;
    queue<int> q;
    sort(vedges.begin(),vedges.end());
    vector<int> vedges_start(hot_cnt+1,0);
    for(int i=(int)vedges.size()-1;i>=0;i--) vedges_start[vedges[i][0]]=i;
    for(int i=1;i<=hot_cnt;i++)
    {
        if(cc_id[i]!=0) continue;
        cc_cnt++;
        auto add=[&](int a)
        {
            if(cc_id[a]==0)
            {
                cc_id[a]=cc_cnt;
                q.push(a);
            }
        };
        add(i);
        while(!q.empty())
        {
            int a=q.front();
            q.pop();
            for(int j=vedges_start[a];j<(int)vedges.size()&&vedges[j][0]==a;j++) add(vedges[j][1]);
        }
    }
    vedges.clear();
    for(int i=1;i<=m;i++)
    {
        auto [a,b]=wall_hots[i];
        vedges.push_back({cc_id[a],cc_id[b]});
        vedges.push_back({cc_id[b],cc_id[a]});
    }
    sort(vedges.begin(),vedges.end());
    for(int i=(int)vedges.size()-1;i>=0;i--) vedges_start[vedges[i][0]]=i;
    vector<int> d(cc_cnt+1,0);
    sort(hot_pos+1,hot_pos+hot_cnt+1);
    auto add=[&](int a,int nd)
    {
        if(d[a]==0)
        {
            d[a]=nd;
            q.push(a);
        }
    };
    for(int i=1;i<=hot_cnt;i++)
    {
        auto [x,y,hot]=hot_pos[i];
        add(cc_id[hot],1);
        while(!q.empty())
        {
            int a=q.front();
            q.pop();
            for(int j=vedges_start[a];j<(int)vedges.size()&&vedges[j][0]==a;j++) add(vedges[j][1],d[a]+1);
        }
    }
    vector<int> res;
    for(int i=1;i<=m;i++)
    {
        auto [a,b]=wall_hots[i];
        if(d[cc_id[a]]==d[cc_id[b]]) res.push_back(i);
    }
    cout << res.size() << "\n";
    for(int w:res) cout << w << "\n";
    return 0;
}

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