Submission #1281604

#	Time	Username	Problem	Language	Result	Execution time	Memory
1281604		red_souls	Fire (BOI24_fire)	C++17	0 / 100	1 ms	580 KiB

Main

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

const int N = 2e5 + 16, INF = 1e9;
int n;
ll m, s[N], e[N];

namespace sub6 {

    pair <ll, ll> a[N];
    vector < pair <ll, ll> > queries;

    ll prefix[N];
    int up[N][26], result = INF;

    int findPos(ll k) {
        int l = 1, r = n, mid, pos = 0;
        while (l <= r) {
            mid = l + r >> 1;
            if (a[mid].first <= k) {
                l = mid + 1;
                pos = mid;
            }
            else {
                r = mid - 1;
            }
        }
        return pos;
    }

    void build() {
        for (int i = 1; i <= n; i++) {
            prefix[i] = max(prefix[i - 1], a[i].second);
        }
        for (int i = 1; i <= n; i++) {
            up[i][0] = findPos(prefix[i] + 1);
            if (up[i][0] <= i) {
                up[i][0] = 0;
            }
        }
        for (int j = 1; j <= 20; j++) {
            for (int i = 1; i <= n; i++) {
                up[i][j] = up[up[i - 1][j]][j];
            }
        }
    }

    int query(pair <ll, ll> target) {
        ll u = target.first, v = target.second;
        int cur = findPos(u), ans = 0;
        if (cur == 0) {
            return -1;
        }
        if (prefix[cur] < u) {
            return -1;
        }
        if (prefix[cur] >= v) {
            return 1;
        }

        for (int i = 20; i >= 0; i--) {
            if (up[cur][i] != 0 && prefix[up[cur][i]] < v) {
                u = up[cur][i];
                ans += (1 << i);
            }
        }
        cur = up[cur][0];
        if (cur == 0) {
            return -1;
        }
        ans += 2;
        return ans;
    }

    void solve() {
        queries.push_back({0, m - 1});
        for (int i = 1; i <= n; i++) {
            if (s[i] > e[i]) {
                queries.push_back({e[i], e[i] + m - 1});
                e[i] += m;
            }
            a[i] = {s[i], e[i]};
        }
        sort(a + 1, a + 1 + n);
        build();
        for (auto x : queries) {
            int ans = query(x);
            if (ans == -1) {
                continue;
            }
            result = min(result, 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];
    }
    sub6 :: solve();

    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:108:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:109:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  109 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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