Submission #692667

#	Time	Username	Problem	Language	Result	Execution time	Memory
692667		sharaelong	Ancient Books (IOI17_books)	C++17	0 / 100	32 ms	59212 KiB

books

#include "books.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

struct DisjointSet {
    int n;
    vector<int> parent, rank;
    DisjointSet(int _n) : n(_n) {
        parent.resize(n);
        iota(parent.begin(), parent.end(), 0);
        rank.resize(n, 0);
    }

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

    void merge(int u, int v) {
        u = find(u); v = find(v);
        if (u == v) return;
        if (rank[u] > rank[v]) swap(u, v);
        parent[u] = v;
        if (rank[u] == rank[v]) ++rank[v];
    }
};

struct FenwickTree {
    vector<int> tree;
    FenwickTree(int size) {
        tree.resize(size+1, 0);
    }

    int sum(int pos) {
        int ret = 0;
        for (int i=pos+1; i>0; i &= (i-1)) ret += tree[i];
        return ret;
    }

    void add(int pos, int val) {
        for (int i=pos+1; i<tree.size(); i+=(i & -i)) tree[i] += val;
    }
};

const int MAX_N = 1e6 + 1;
const ll INF = 4e18;

DisjointSet dsu(MAX_N);
FenwickTree fen(MAX_N);
bool visited[MAX_N];
vector<int> cycle[MAX_N];
vector<int> adj[MAX_N];
ll dp[MAX_N];

void dfs(int here, int parent = -1) {
    bool merged = false;
    if (parent != -1) {
        int mn = *min_element(cycle[here].begin(), cycle[here].end());
        int mx = *max_element(cycle[here].begin(), cycle[here].end());
        if (fen.sum(mx) - fen.sum(mn) > 0) {
            dsu.merge(here, parent);
            for (int x: cycle[here]) fen.add(x, 1);
            if (cycle[here].size() > cycle[parent].size()) swap(cycle[here], cycle[parent]);
            for (int x: cycle[here]) cycle[parent].push_back(x);
            merged = true;
        }
    }
    
    if (!merged) {
        for (int x: cycle[here]) fen.add(x, 1);
    }
    for (int there: adj[here]) {
        dfs(there, here);
    }
    if (!merged) {
        for (int x: cycle[dsu.find(here)]) fen.add(x, -1);
    }
}

ll minimum_walk(vector<int> p, int s) {
    int n = p.size();
    vector<pii> range;
    ll jump_len = 0;
    for (int i=0; i<n; ++i) {
        if (!visited[i]) {
            int l = i, r = i;
            jump_len += abs(i-p[i]);
            visited[i] = true;
            int x = p[i];
            while (x != i) {
                l = min(l, x);
                r = max(r, x);
                jump_len += abs(x-p[x]);
                visited[x] = true;
                dsu.merge(x, i);
                x = p[x];
            }
            range.push_back({ l+1, i });
            range.push_back({ -r-1, i });
        }
    }
    
    sort(range.begin(), range.end(), [](const pii& a, const pii& b) {
        return abs(a.first) < abs(b.first);
    });
    vector<pii> st;
    for (auto[x, idx]: range) {
        // cout << x << ' ' << idx << endl;
        if (x >= 0) {
            st.push_back({ idx, 1 });
        } else {
            int remove_cnt = 0;
            while (dsu.find(st.back().first) != dsu.find(idx)) {
                dsu.merge(st.back().first, idx);
                remove_cnt++;
            }
            assert(!st.empty() && dsu.find(st.back().first) == dsu.find(idx));
            st.back().second += remove_cnt-1;
            if (st.back().second <= 0) st.pop_back();
        }
    }
    
    vector<pair<pii, int>> dfs_order;
    for (int i=0; i<n; ++i) cycle[dsu.find(i)].push_back(i);
    for (int i=0; i<n; ++i) {
        if (dsu.find(i) == i) {
            dfs_order.push_back({ { cycle[i][0], cycle[i].back() }, i });
        }
    }
    sort(dfs_order.begin(), dfs_order.end());
    
    st.clear();
    vector<int> roots;
    for (int i=0; i<dfs_order.size(); ++i) {
        while (!st.empty() && st.back().first < dfs_order[i].first.first) {
            st.pop_back();
        }
        if (!st.empty()) {
            adj[st.back().second].push_back(dfs_order[i].second);
            // cout << st.back().second << ' ' << dfs_order[i].second << endl;
        }
        if (st.empty()) roots.push_back(dfs_order[i].second);
        st.push_back({ dfs_order[i].first.second, dfs_order[i].second });
    }
    for (int r: roots) dfs(r);

    ll accum = s;
    // for (int i=0; i<n; ++i) {
    //     if (dsu.find(i) == i && cycle[i].size() >= 2) {
    //         ll l = INF, r = INF;
    //         for (int x: cycle[i]) {
    //             if (x <= s) l = min(l, (ll)s-x);
    //             if (x >= s) r = min(r, (ll)x-s);
    //         }
    //         cout << i << ' ' << l << ' ' << r << endl;
    //         if (l > INF/2) accum = max(accum, s+r);
    //         else dp[s-l] = s+r;
    //     }
    // }
    for (int root: roots) {
        ll l = INF, r = INF;
        for (int x: cycle[root]) {
            if (x <= s) l = min(l, (ll)s-x);
            if (x >= s) r = min(r, (ll)x-s);
        }
        // cout << root << ' ' << l << ' ' << r << endl;
        if (l > INF/2) accum = max(accum, s+r);
        else dp[s-l] = s+r;
    }
    
    ll ans = INF;
    for (int i=0; i<=s; ++i) {
        // cout << i << ' ' << accum << endl;
        ans = min(ans, accum-i);
        accum = max(accum, dp[i]);
    }
    // cout << jump_len << endl;
    return jump_len + 2 * ans;
}

Compilation message (stderr)

books.cpp: In member function 'void FenwickTree::add(int, int)':
books.cpp:42:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |         for (int i=pos+1; i<tree.size(); i+=(i & -i)) tree[i] += val;
      |                           ~^~~~~~~~~~~~
books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:135:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<std::pair<int, int>, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  135 |     for (int i=0; i<dfs_order.size(); ++i) {
      |                   ~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 12
• Subtask 2: 0 / 10
• Subtask 3: 0 / 28
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30