Submission #532555

#	Time	Username	Problem	Language	Result	Execution time	Memory
532555		wiwiho	Fences (JOI18_fences)	C++14	51 / 100	340 ms	262148 KiB

fences

#include <bits/stdc++.h>
#include <bits/extc++.h>

#define StarBurstStream ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define iter(a) a.begin(), a.end()
#define riter(a) a.rbegin(), a.rend()
#define lsort(a) sort(iter(a))
#define gsort(a) sort(riter(a))
#define pb(a) push_back(a)
#define eb(a) emplace_back(a)
#define pf(a) push_front(a)
#define ef(a) emplace_front(a)
#define pob pop_back()
#define pof pop_front()
#define mp(a, b) make_pair(a, b)
#define F first
#define S second
#define mt make_tuple
#define gt(t, i) get<i>(t)
#define tomax(a, b) ((a) = max((a), (b)))
#define tomin(a, b) ((a) = min((a), (b)))
#define topos(a) ((a) = (((a) % MOD + MOD) % MOD))
#define uni(a) a.resize(unique(iter(a)) - a.begin())
#define printv(a, b) {bool pvaspace=false; \
for(auto pva : a){ \
    if(pvaspace) b << " "; pvaspace=true;\
    b << pva;\
}\
b << "\n";}

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;
using tiii = tuple<int, int, int>;

const ll MOD = 1000000007;
const ll MAX = 2147483647;

template<typename A, typename B>
ostream& operator<<(ostream& o, pair<A, B> p){
    return o << '(' << p.F << ',' << p.S << ')';
}

ll ifloor(ll a, ll b){
    if(b < 0) a *= -1, b *= -1;
    if(a < 0) return (a - b + 1) / b;
    else return a / b;
}

ll iceil(ll a, ll b){
    if(b < 0) a *= -1, b *= -1;
    if(a > 0) return (a + b - 1) / b;
    else return a / b;
}

using pdd = pair<ld, ld>;
ld eps = 1e-9;

pdd operator+(pdd a, pdd b){
    return mp(a.F + b.F, a.S + b.S);
}

pdd operator-(pdd a, pdd b){
    return mp(a.F - b.F, a.S - b.S);
}

ld dot(pdd a, pdd b){
    return a.F * b.F + a.S * b.S;
}

ld cross(pdd a, pdd b){
    return a.F * b.S - a.S * b.F;
}

ld abs2(pdd a){
    return a.F * a.F + a.S * a.S;
}

ld abs(pdd a){
    return sqrt(abs2(a));
}

pdd operator*(ld i, pdd p){
    return mp(i * p.F, i * p.S);
}

int ori(pdd a, pdd b){
    if(abs(cross(a, b)) <= eps) return 0;
    else if(cross(a, b) > 0) return 1;
    else return -1;
}

bool intersect(pdd a, pdd b, pdd c, pdd d){
    return ori(b - a, c - a) * ori(b - a, d - a) < 0 && ori(d - c, a - c) * ori(d - c, b - c) < 0;
}

bool canproj(pdd p, pdd a, pdd b){
    return dot(b - a, p - a) >= 0 && dot(a - b, p - b) >= 0;
}

pdd getproj(pdd p, pdd a, pdd b){
    if(abs2(a - b) <= eps) return a;
    return a + dot(p - a, b - a) / abs2(b - a) * (b - a);
}

pdd v1 = mp(0, 0), v2 = mp(48763, 3234234);

struct Line{
    pdd a, b;
};

struct edge{
    int to;
    ld w;
    int f;
};

ostream& operator<<(ostream& o, edge e){
    return o << '(' << e.to << ',' << e.w << ',' << e.f << ')';
}

int n;
ld S;
vector<Line> border;
vector<Line> e;
vector<pdd> pos;
vector<vector<int>> ps;
vector<vector<edge>> g;
int ts;

void init(){
    cin >> n >> S;
    e.resize(n);
    for(int i = 0; i < n; i++){
        cin >> e[i].a.F >> e[i].a.S >> e[i].b.F >> e[i].b.S;
    }
    border.eb(Line({mp(S, S), mp(S, -S)}));
    border.eb(Line({mp(-S, -S), mp(S, -S)}));
    border.eb(Line({mp(-S, -S), mp(-S, S)}));
    border.eb(Line({mp(S, S), mp(-S, S)}));
    border.eb(Line({mp(S, -S), mp(-S, S)}));
    border.eb(Line({mp(-S, -S), mp(S, S)}));
    e.eb(Line({mp(S, S), mp(S, S)}));
    e.eb(Line({mp(S, -S), mp(S, -S)}));
    e.eb(Line({mp(-S, S), mp(-S, S)}));
    e.eb(Line({mp(-S, -S), mp(-S, -S)}));
    n += 4;
    ps.resize(n);
}

bool check(pdd a, pdd b){
    for(auto i : border){
        if(intersect(a, b, i.a, i.b)) return false;
    }
    return true;
}

bool foxyy(pdd a, pdd b){
    return intersect(a, b, v1, v2);
}

void addedge(int x, pdd a, int y, pdd b){
    if(!check(a, b)){
        //cerr << "qq " << a << " " << b << "\n";
        return;
    }
    int av = ts++;
    int bv = ts++;
    pos.eb(a);
    pos.eb(b);
    g.eb(); g.eb();
    //cerr << "addedge " << x << " " << av << " " << y << " " << bv << "\n";
    ps[x].eb(av); ps[y].eb(bv);
    g[av].eb(edge({bv, abs(a - b), foxyy(a, b)}));
    g[bv].eb(edge({av, abs(a - b), foxyy(a, b)}));
    //cerr << "addedge " << a << " " << b << " " << abs(a - b) << " " << foxyy(a, b) << "\n";
}

void tryproj(int x, pdd p, int y, pdd a, pdd b){
    if(!canproj(p, a, b)) return;
    //cerr << "canproj " << x << " " << p << " " << y << " " << getproj(p, a, b) << "\n";
    addedge(x, p, y, getproj(p, a, b));
}

void buildedges(int x, int y){
    addedge(x, e[x].a, y, e[y].a);
    addedge(x, e[x].b, y, e[y].a);
    addedge(x, e[x].a, y, e[y].b);
    addedge(x, e[x].b, y, e[y].b);
    
    tryproj(x, e[x].a, y, e[y].a, e[y].b);
    tryproj(x, e[x].b, y, e[y].a, e[y].b);
    tryproj(y, e[y].a, x, e[x].a, e[x].b);
    tryproj(y, e[y].b, x, e[x].a, e[x].b);
}

void buildline(int id){
    for(int i : ps[id]){
        for(int j : ps[id]){
            g[i].eb(edge({j, 0, foxyy(pos[i], pos[j])}));
        }
    }
}

struct info{
    ld d;
    int v;
    int f;

    bool operator<(info b) const{
        return d > b.d;
    }
};

ld calc(int s){
    std::priority_queue<info> pq;
    vector<vector<ld>> dis(2, vector<ld>(ts, 1e20));
    dis[0][s] = 0;
    pq.push(info({0, s, 0}));
    while(!pq.empty()){
        ld d = pq.top().d;
        int v = pq.top().v, f = pq.top().f;
        pq.pop();
        if(abs(d - dis[f][v]) > eps) continue;
        for(auto i : g[v]){
            int nf = f ^ i.f;
            if(d + i.w >= dis[nf][i.to]) continue;
            dis[nf][i.to] = d + i.w;
            pq.push(info({d + i.w, i.to, nf}));
        }
    }
    //cerr << "calc " << s << " " << dis[1][s] << "\n";
    return dis[1][s];
}

int main(){
    StarBurstStream

    init();

    for(int i = 0; i < n; i++){
        for(int j = i + 1; j < n; j++) buildedges(i, j);
    }
    for(int i = 0; i < n; i++) buildline(i);

    /*cerr << "graph\n";
    for(int i = 0; i < ts; i++){
        cerr << i << " " << pos[i] << "  ";
        printv(g[i], cerr);
    }*/

    ld ans = 1e20;
    for(int i = 0; i < ts; i++){
        ans = min(ans, calc(i));
    }
    cout << fixed << setprecision(20) << ans << "\n";

    return 0;
}

• Subtask 1: 18 / 18
• Subtask 2: 33 / 33
• Subtask 3: 0 / 49