제출 #503826

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
503826		tabr	Islands (IOI08_islands)	C++17	100 / 100	795 ms	128400 KiB

islands

#include <bits/stdc++.h>
using namespace std;
#ifdef tabr
#include "library/debug.cpp"
#else
#define debug(...)
#endif

const int N = (int) 1e6;
int l[N];
int nxt[N];
long long dist[N];
long long max_dist[N];
bool cycle[N];
bool was[N];
vector<int> g[N];
int p[N];
pair<int, long long> deq[N * 2];

int dsu_get(int x) {
    if (p[x] == x) {
        return x;
    } else {
        return p[x] = dsu_get(p[x]);
    }
}

bool dsu_unite(int x, int y) {
    x = dsu_get(x);
    y = dsu_get(y);
    if (x == y) {
        return false;
    }
    p[x] = y;
    return true;
}

int x[N];
int order[N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    iota(p, p + n, 0);
    for (int i = 0; i < n; i++) {
        int j;
        cin >> j >> l[i];
        j--;
        g[j].emplace_back(i);
        dsu_unite(i, j);
        nxt[i] = j;
    }
    long long ans = 0;
    for (int i = 0; i < n; i++) {
        if (i != dsu_get(i)) {
            continue;
        }
        int c = i;
        while (!was[c]) {
            was[c] = 1;
            c = nxt[c];
        }
        int u = nxt[c];
        cycle[c] = 1;
        int sz = 1;
        x[0] = c;
        while (u != c) {
            cycle[u] = 1;
            x[sz++] = u;
            u = nxt[u];
        }
        int sz2 = 0;
        int beg = 0;
        int end = 0;
        for (int jj = 0; jj < sz; jj++) {
            int j = x[jj];
            deq[end++].first = j;
            while (beg < end) {
                int v = deq[beg++].first;
                order[sz2++] = v;
                for (int to : g[v]) {
                    if (cycle[to]) {
                        continue;
                    }
                    dist[to] = dist[v] + l[to];
                    deq[end++].first = to;
                }
            }
        }
        long long t = 0;
        for (int j = sz2 - 1; j >= 0; j--) {
            int v = order[j];
            max_dist[v] = max(max_dist[v], dist[v]);
            if (cycle[v]) {
                continue;
            }
            int to = nxt[v];
            t = max(t, max_dist[to] + max_dist[v] - dist[to] * 2);
            max_dist[to] = max(max_dist[to], max_dist[v]);
        }
        long long y = l[c];
        beg = end = 0;
        deq[end++] = make_pair(0, 0);
        for (int jj = 1; jj < sz * 2; jj++) {
            int j = jj % sz;
            if (x[deq[beg].first] == x[j]) {
                beg++;
            }
            t = max(t, y + max_dist[x[j]] - deq[beg].second);
            long long z = y - max_dist[x[j]];
            while (beg < end && deq[end - 1].second >= z) {
                end--;
            }
            y += l[x[j]];
            deq[end++] = make_pair(j, z);
        }
        ans += t;
    }
    cout << ans << '\n';
    return 0;
}

• Subtask 1: 33 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10