oj.uz

답안 #488926

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
488926 2021-11-20T19:50:59 Z dxz05 Islands (IOI08_islands) C++14
80 / 100
 1257 ms 131076 KB 
//#pragma GCC optimize("Ofast,O2,O3,unroll-loops")
//#pragma GCC target("avx2")

#include <iostream>
#include <vector>
#include <bitset>
#include <stack>
#include <algorithm>
#include <chrono>
#include <random>

using namespace std;

#define SZ(s) ((int)s.size())
#define all(x) (x).begin(), (x).end()
#define lla(x) (x).rbegin(), (x).rend()

#define MP make_pair

typedef long long ll;
const double eps = 0.000001;
const int MOD = 998244353;
const int INF = 1000000101;
const long long LLINF = 1223372000000000555;
const int N = 1e6 + 1;
const int M = 222;

mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

int f[N]; int w[N];
bitset<N> used;
stack<int> st;

vector<int> cycle;

void dfs0(int v){
    if (!cycle.empty()) return;
    used[v] = true;
    st.push(v);

    if (used[f[v]]){
        while (!st.empty()){
            int x = st.top(); st.pop();
            cycle.push_back(x);
            if (x == f[v]) break;
        }
        return;
    }
    if (!cycle.empty()) return;

    dfs0(f[v]);

    if (!st.empty()) st.pop();
}

int parent[N];
int find(int x){
    return (x == parent[x] ? x : parent[x] = find(parent[x]));
}

vector<int> g[N];

bitset<N> incycle;

int A(int u, int v){
    if (f[u] == v && f[v] != u) return w[u];
    if (f[u] != v && f[v] == u) return w[v];
    return max(w[u], w[v]);
}

void dfs(int v, int p, ll d, int root, vector<int> &tree, vector<ll> &dist, bool flag){
    tree.push_back(v);
    dist.push_back(d);
    for (int u : g[v]){
        if (u != p){
            if (u == root || !incycle[u]) dfs(u, v, d + A(u, v), root, tree, dist, flag);
        }
    }
    if (flag) g[v].clear();
}

ll arr[N];

ll component(int root){
    cycle.clear();
    while (!st.empty()) st.pop();

    dfs0(root);

    for (int v : cycle){
        incycle[v] = true;
    }

    ll ans = 0;
    vector<int> tree; vector<ll> dist;
    for (int v : cycle){
        dfs(v, v, 0, v, tree, dist, false);

        int i = max_element(all(dist)) - dist.begin();
        ans = max(ans, dist[i]);
        arr[v] = dist[i];

        tree.clear(); dist.clear();
        dfs(tree[i], tree[i], 0, v, tree, dist, true);

        ans = max(ans, *max_element(all(dist)));
        tree.clear(), dist.clear();
    }

    int n = cycle.size();

    if (n == 2){
        int u = cycle[0], v = cycle[1];
        ans = max(ans, arr[u] + arr[v] + A(u, v));
        return ans;
    }

    vector<ll> a(n);
    a[0] = {arr[cycle[0]]};
    ll sum = 0;
    for (int i = 1; i < n; i++){
        sum += A(cycle[i - 1], cycle[i]);
        a[i] = arr[cycle[i]] + sum;
    }
    sum += A(cycle[0], cycle.back());

//    for (int x : cycle) cout << x << ' '; cout << endl;
//    for (ll x : a) cout << x << ' '; cout << endl;

    ans = max(ans, arr[cycle[0]] + *max_element(a.begin() + 1, a.end()));

    vector<ll> sf(n, a.back());
    for (int i = n - 2; i >= 0; i--) sf[i] = max(sf[i + 1], a[i]);

    ll add = 0;
    int v, u;
    ll mx = 0;
    for (int i = 1; i < n; i++){
        v = cycle[i], u = cycle[i - 1];
        add -= A(v, u);
        mx = max(mx, a[i - 1] + sum);

        ans = max(ans, arr[v] + add + mx);
        if (i + 1 < n) ans = max(ans, arr[v] + add + sf[i + 1]);
        mx = max(mx, a[i]);

//        for (int j = 1; j <= n; j++) cout << ST.get(j, j) << ' '; cout << endl;
    }

    return ans;
}

void solve(int TC) {
    int n;
    cin >> n;

    for (int i = 1; i <= n; i++) parent[i] = i;

    for (int i = 1; i <= n; i++){
        cin >> f[i] >> w[i];
        if (rng() & 1) parent[find(i)] = find(f[i]); else
            parent[find(f[i])] = find(i);
        if (f[f[i]] != i){
            g[i].emplace_back(f[i]);
            g[f[i]].emplace_back(i);
        }
    }

    bitset<N> comp;

    ll ans = 0;
    for (int i = 1; i <= n; i++){
        if (!comp[find(i)]){
            comp[find(i)] = true;
            ll cur = component(i);
            ans += cur;
        }
    }

    cout << ans;

}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);

#ifdef dddxxz
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    int TC = 1;
//    cin >> TC;

    for (int test = 1; test <= TC; test++) {
        //debug(test);
        //cout << "Case #" << test << ": ";
        solve(test);
    }

    return 0;
}

Subtask #1
33.0 / 33.0

# 결과 실행 시간 메모리 Grader output
1 Correct 13 ms 23884 KB Output is correct
2 Correct 13 ms 23884 KB Output is correct
3 Correct 13 ms 23936 KB Output is correct
4 Correct 14 ms 23936 KB Output is correct
5 Correct 13 ms 23960 KB Output is correct
6 Correct 12 ms 23884 KB Output is correct
7 Correct 13 ms 23968 KB Output is correct
8 Correct 14 ms 23844 KB Output is correct
9 Correct 12 ms 23884 KB Output is correct
10 Correct 14 ms 23976 KB Output is correct
11 Correct 14 ms 23884 KB Output is correct

Subtask #2
3.0 / 3.0

# 결과 실행 시간 메모리 Grader output
1 Correct 17 ms 24012 KB Output is correct
2 Correct 14 ms 24008 KB Output is correct

Subtask #3
4.0 / 4.0

# 결과 실행 시간 메모리 Grader output
1 Correct 14 ms 24024 KB Output is correct
2 Correct 15 ms 24384 KB Output is correct

Subtask #4
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 20 ms 24908 KB Output is correct
2 Correct 30 ms 27460 KB Output is correct
3 Correct 23 ms 25312 KB Output is correct
4 Correct 18 ms 24524 KB Output is correct

Subtask #5
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 34 ms 28908 KB Output is correct
2 Correct 47 ms 31048 KB Output is correct

Subtask #6
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 83 ms 36804 KB Output is correct
2 Correct 102 ms 44196 KB Output is correct
3 Correct 131 ms 54608 KB Output is correct

Subtask #7
10.0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 149 ms 46164 KB Output is correct
2 Correct 231 ms 73200 KB Output is correct
3 Correct 255 ms 84628 KB Output is correct
4 Correct 265 ms 102420 KB Output is correct

Subtask #8
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Correct 316 ms 84760 KB Output is correct
2 Correct 877 ms 131072 KB Output is correct
3 Correct 288 ms 66772 KB Output is correct
4 Correct 364 ms 107380 KB Output is correct
5 Correct 409 ms 108160 KB Output is correct
6 Correct 1257 ms 77604 KB Output is correct
7 Runtime error 366 ms 131076 KB Execution killed with signal 9

Subtask #9
0 / 10.0

# 결과 실행 시간 메모리 Grader output
1 Runtime error 347 ms 131076 KB Execution killed with signal 9
2 Halted 0 ms 0 KB -