Submission #40852

#	Time	Username	Problem	Language	Result	Execution time	Memory
40852		grumpy_gordon	Port Facility (JOI17_port_facility)	C++14	100 / 100	1571 ms	119396 KiB

port_facility

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#include <bits/stdc++.h>

//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
//#pragma GCC target("avx,tune=native")
//float __attribute__((aligned(32)))

using namespace std;

typedef long long ll;

typedef unsigned long long ull;

typedef long double ld;

int mysqrt(ll x){
    int l = 0, r = 1e9 + 1;
    while (r - l > 1){
        int m = (l + r) / 2;
        if (m * (ll)m <= x)
            l = m;
        else
            r = m;
    }
    return l;
}

mt19937 rnd(1337);

ll AR = 19, BR = 13, CR = 23, XR = 228, YR = 322, MODR = 1e9 + 993;

ll myrand(){
    ll ZR = (XR * AR + YR * BR + CR) % MODR;
    XR = YR;
    YR = ZR;
    return ZR;
}

const int Mod = 1e9 + 7;

int bpow(int x, int y){
    if (y == 0)
        return 1;
    if (y == 1)
        return x;
    int ret = bpow(x, y >> 1);
    ret = (ret * (ll)ret) % Mod;
    if (y & 1)
        ret = (ret * (ll)x) % Mod;
    return ret;
}

int bdiv(int x, int y){
    return (x * (ll)bpow(y, Mod - 2)) % Mod;
}

void setmin(int &x, int y){
    x = min(x, y);
}

void setmax(int &x, int y){
    x = max(x, y);
}

void setmin(ll &x, ll y){
    x = min(x, y);
}

void setmax(ll &x, ll y){
    x = max(x, y);
}

int gcd(int a, int b){
    return a ? gcd(b % a, a) : b;
}

const ll llinf = 2e18 + 100;

const int maxn = 2e5 + 100, maxw = 1e6 + 100, inf = 2e9 + 100, sq = 300, mod = 1e9 + 7, LG = 17;

pair<int, int> a[maxw];

int arr[2 * maxw];

int n;

vector<pair<int, int> > w;

int p[maxw];

int r[maxw];

int get(int x){
    return x == p[x] ? x : p[x] = get(p[x]);
}

void uni(int x, int y){
    x = get(x);
    y = get(y);
    if (x == y)
        return;
    if (r[x] < r[y])
        swap(x, y);
    p[y] = x;
    if (r[x] == r[y])
        r[x]++;
}

bool used[maxw];

vector<int> e[maxw];

int col[maxw];

bool dfs(int v, int cs = 0){
    col[v] = cs;
    used[v] = 1;
    for (auto i : e[v])
    if (!used[i]){
        if (dfs(i, cs ^ 1))
            return 1;
    }
    else
    if (col[i] != (cs ^ 1))
        return 1;
    return 0;
}

int main()
{
    #ifdef ONPC
    //ifstream cin("a.in");
    //ofstream cout("a.out");
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
    #else
    //ifstream cin("sprinklers.in");
    //ofstream cout("sprinklers.out");
    //freopen("road.in", "r", stdin);
    //freopen("road.out", "w", stdout);
    #endif // ONPC
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n;
    for (int i = 0; i < n; i++){
        cin >> a[i].first >> a[i].second;
        a[i].first--;
        a[i].second--;
        arr[a[i].first] = i;
        arr[a[i].second] = -1;
    }
    for (int i = 0; i < n; i++)
        p[i] = i;
    /*
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++)
            if (a[i].first < a[j].first && a[i].second > a[j].first && a[i].second < a[j].second)
                uni(i, j);
    */
    stack<int> q;
    stack<int> g;
    for (int i = 0; i < 2 * n; i++){
        if (arr[i] < 0){
            q.pop();
            int last = (q.empty() ? inf : a[q.top()].second);
            vector<int> vsp;
            while (!g.empty() && a[g.top()].second < last)
                vsp.push_back(g.top()), g.pop();
            reverse(vsp.begin(), vsp.end());
            for (auto j : vsp)
                q.push(j);
            continue;
        }
        int id = arr[i];
        if (!g.empty() && a[id].second > a[g.top()].second){
            cout << 0;
            return 0;
        }
        int last = -1;
        stack<int> vsp;
        while (!q.empty() && a[q.top()].second < a[id].second){
            if (last != -1){
                if (get(last) == get(q.top()))
                    break;
                uni(last, q.top());
            }
            else
                last = q.top();
            vsp.push(q.top());
            q.pop();
        }
        if (last != -1)
            w.push_back(make_pair(last, id)), g.push(id);
        else
            q.push(id);
        while (!vsp.empty())
            q.push(vsp.top()), vsp.pop();
    }
    for (auto it : w)
    if (get(it.first) == get(it.second)){
        cout << 0;
        return 0;
    }
    for (auto it : w)
        e[get(it.first)].push_back(get(it.second)), e[get(it.second)].push_back(get(it.first));
    int ans = 1;
    for (int i = 0; i < n; i++)
    if (!used[get(i)])
    if (dfs(get(i))){
        cout << 0;
        return 0;
    }
    else
        ans = (ans * 2) % mod;
    cout << ans;
}

Compilation message (stderr)

port_facility.cpp: In function 'int main()':
port_facility.cpp:295:8: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
     if (!used[get(i)])
        ^

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 56 / 56
• Subtask 4: 22 / 22