제출 #1281436

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1281436		red_souls	Fire (BOI24_fire)	C++17	40 / 100	161 ms	42808 KiB

Main

#include <bits/stdc++.h>
#define ll long long
#define task "FIRE"
using namespace std;

const int N = 1e6 + 16;
const ll INF = 1e18;
int n, m;
ll s[N], e[N];

namespace sub3 {
    ll cnt, result = INF;
    pair <ll, ll> a[N];

    vector < pair <ll, ll> > checkLines;

    bool cmp(pair <ll, ll> a, pair <ll, ll> b) {
        if (a.first == b.first) {
            return a.second > b.second;
        }
        return a.first < b.first;
    }

    ll query(pair <ll, ll> target) {
        ll curP = 1, p = target.first, cnt = 0;
        while (p <= target.second) {
            ll r = -1;
            while (curP <= n && a[curP].first <= p) {
                r = max(a[curP].second, r);
                curP++;
            }
            if (r < p) {
                return -1;
            }
            p = r + 1;
            cnt++;
        }
        return cnt;
    }

    void solve() {
        checkLines.push_back({0, m - 1});
        for (int i = 1; i <= n; i++) {
            if (s[i] > e[i]) {
                checkLines.push_back({e[i], e[i] + m - 1});
                e[i] += m;
            }
            a[i] = {s[i], e[i] - 1};
        }
        sort(a + 1, a + 1 + n, cmp);
        for (auto x : checkLines) {
            ll ans = query(x);
            if (ans == -1) {
                continue;
            }
            result = min(result, ans);
        }
        if (result == INF) {
            result = -1;
        }
        cout << result;
    }
}

namespace sub6 {
    ll result = INF;
    pair<ll,ll> a[N];
    vector<pair<ll,ll>> checkLines;
    int maxx = 0;
    const int LOG = 22; // đủ cho up to ~4M

    void compress() {
        vector<ll> c;
        for (int i = 1; i <= n; i++) {
            c.push_back(a[i].first);
            c.push_back(a[i].second);
        }
        for (auto x : checkLines) {
            c.push_back(x.first);
            c.push_back(x.second);
        }
        sort(c.begin(), c.end());
        c.erase(unique(c.begin(), c.end()), c.end());
        for (int i = 1; i <= n; i++) {
            a[i].first = lower_bound(c.begin(), c.end(), a[i].first) - c.begin() + 1;
            a[i].second = lower_bound(c.begin(), c.end(), a[i].second) - c.begin() + 1;
            maxx = max(maxx, (int)a[i].first);
            maxx = max(maxx, (int)a[i].second);
        }
        for (auto &x : checkLines) {
            x.first = lower_bound(c.begin(), c.end(), x.first) - c.begin() + 1;
            x.second = lower_bound(c.begin(), c.end(), x.second) - c.begin() + 1;
            maxx = max(maxx, (int)x.first);
            maxx = max(maxx, (int)x.second);
        }
    }

    static int maxR_idx[N];
    static int up[N][LOG];

    void solve() {
        checkLines.clear();
        checkLines.push_back({0, m - 1});
        for (int i = 1; i <= n; i++) {
            if (s[i] > e[i]) {
                checkLines.push_back({e[i], e[i] + m - 1});
                e[i] += m;
            }
            a[i] = {s[i], e[i] - 1};
        }
        compress();

        // reset arrays up to maxx+1
        for (int i = 0; i <= maxx + 1; i++) {
            maxR_idx[i] = 0;
            for (int j = 0; j < LOG; j++) up[i][j] = maxx + 1;
        }

        // maxR_idx[pos] = furthest right index reachable when starting at position pos
        for (int i = 1; i <= n; i++) {
            int L = (int)a[i].first;
            int R = (int)a[i].second;
            maxR_idx[L] = max(maxR_idx[L], R);
        }
        // prefix max so maxR_idx[i] = best reachable from any interval that starts <= i
        for (int i = 1; i <= maxx; i++) {
            maxR_idx[i] = max(maxR_idx[i - 1], maxR_idx[i]);
        }

        // define next position after taking one interval starting at pos:
        // nxt[pos] = maxR_idx[pos] + 1  (if maxR_idx[pos] < pos then impossible from pos)
        for (int i = 1; i <= maxx; i++) {
            up[i][0] = min(maxx + 1, maxR_idx[i] + 1);
        }
        up[maxx + 1][0] = maxx + 1; // sentinel

        // build binary lifting table
        for (int j = 1; j < LOG; j++) {
            for (int i = 1; i <= maxx + 1; i++) {
                up[i][j] = up[ up[i][j - 1] ][ j - 1 ];
            }
        }

        // answer queries for each check line
        for (auto x : checkLines) {
            int u = (int)x.first, v = (int)x.second;
            if (u < 1 || v < 1 || u > maxx || v > maxx) {
                // if compressed indices out of range skip (shouldn't happen)
            }
            if (u > v) continue;
            // if even the best coverage from u doesn't reach u, impossible
            if (maxR_idx[u] < u) continue;

            int pos = u;
            int ans = 0;
            // jump as much as possible while still <= v
            for (int j = LOG - 1; j >= 0; j--) {
                if (up[pos][j] <= v) {
                    pos = up[pos][j];
                    ans += (1 << j);
                }
            }
            // after jumps, if pos <= v we still need one more interval
            if (pos <= v) ans++;

            result = min(result, 1LL * ans);
        }

        if (result == INF) result = -1;
        cout << result;
    }
}


int main() {
    ios_base :: sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> s[i] >> e[i];
    }
    if (n <= 5000) {
        sub3 :: solve();
    }
    else {
        sub6 :: solve();
    }

    return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

Main.cpp: In function 'int main()':
Main.cpp:181:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  181 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:182:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  182 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 14 / 14
• Subtask 2: 17 / 17
• Subtask 3: 9 / 9
• Subtask 4: 0 / 13
• Subtask 5: 0 / 21
• Subtask 6: 0 / 26