Submission #899632

#	Time	Username	Problem	Language	Result	Execution time	Memory
899632		Szil	Longest Trip (IOI23_longesttrip)	C++17	70 / 100	35 ms	1228 KiB

longesttrip

#include <bits/stdc++.h>
#include "longesttrip.h"

using namespace std;

vector<int> solve3(int N) {
    vector<int> ans(N);
    iota(ans.begin(), ans.end(), 0);
    return ans;
}

vector<int> solve2(int N) {
    queue<int> q;
    vector<int> ans;
    for (int i = 0; i < N; i++) {
        q.push(i);
    }
    int extra = -1;
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        ans.emplace_back(u);
        if (q.empty()) continue;

        int v = q.front();
        if (!are_connected({u}, {v})) {
            q.pop();
            if (q.empty()) {
                extra = v;
            } else {
                q.push(v);
            }
        }
    }
    vector<int> res;
    for (int i = 0; i < ans.size(); i++) {
        if (i == 0 && extra != -1) res.emplace_back(extra);
        res.emplace_back(ans[i]);
    }
    for (int i = 1; i < res.size(); i++) {
        assert(are_connected({res[i-1]}, {res[i]}));
    }
    assert(res.size() == N);
    return res;
}

vector<int> merge_vectors(const vector<int> &a, const vector<int> &b) {
    vector<int> res;
    for (int i : a) res.emplace_back(i);
    for (int i : b) res.emplace_back(i);
    return res;
}

vector<int> get_interval(const vector<int> &a, int l, int r) {
    vector<int> res;
    for (int i = l; i <= r; i++) {
        res.emplace_back(a[i]);
    }
    return res;
}

int find_connection(const vector<int> &a, const vector<int> &b) {
    int lo = 0, hi = a.size() - 1;
    while (lo < hi) {
        int mid = (lo + hi) / 2;
        if (are_connected(get_interval(a, lo, mid), b)) {
            hi = mid;
        } else {
            lo = mid + 1;
        }
    }
    return lo;
}

vector<int> add_to_component(vector<int> comp, int u) {
    if (comp.empty()) return {u};
    if (comp.size() == 1) return {comp.front(), u};

    // TODO remove this and only check with binary search
    if (are_connected({comp.back()}, {u})) {
        return merge_vectors(comp, {u});
    }

    int idx = find_connection(comp, {u});

    if (idx == 0) {
        return merge_vectors({u}, comp);
    }

    vector<int> res1 = {u, comp[idx]};
    auto res2 = merge_vectors(res1, get_interval(comp, idx+1, comp.size()-1));
    auto res3 = merge_vectors(res2, get_interval(comp, 0, idx-1));

    return res3;
}

vector<int> solve1(int N) {
    vector<int> a = {0}, b;

    for (int i = 1; i < N; i++) {
        if (are_connected(a, {i})) {
            a = add_to_component(a, i);
        } else {
            b = add_to_component(b, i);
        }
    }
    if (b.size() > 0 && are_connected(a, b)) {
        if (are_connected({a.front()}, {b.front()})) {
            reverse(a.begin(), a.end());
            return merge_vectors(a, b);
        }
        if (are_connected({a.back()}, {b.front()})) {
            return merge_vectors(a, b);
        }
        if (are_connected({a.front()}, {b.back()})) {
            reverse(a.begin(), a.end());
            reverse(b.begin(), b.end());
            return merge_vectors(a, b);
        }
        if (are_connected({a.back()}, {b.back()})) {
            reverse(b.begin(), b.end());
            return merge_vectors(a, b);
        }

        int idx_in_a = find_connection(a, b);
        int idx_in_b = find_connection(b, a);

        auto res1 = get_interval(a, idx_in_a+1, a.size()-1);
        auto res2 = merge_vectors(res1, get_interval(a, 0, idx_in_a));
        auto res3 = merge_vectors(res2, get_interval(b, idx_in_b, b.size()-1));
        auto res4 = merge_vectors(res3, get_interval(b, 0, idx_in_b-1));

        return res4;
    } else {
        if (a.size() > b.size()) return a;
        else return b;
    }
}

vector<int> longest_trip(int N, int D)
{
    
    if (D == 3) return solve3(N);
    if (D == 2) return solve2(N);
    if (D == 1) return solve1(N);
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> solve2(int)':
longesttrip.cpp:36:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |     for (int i = 0; i < ans.size(); i++) {
      |                     ~~^~~~~~~~~~~~
longesttrip.cpp:40:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     for (int i = 1; i < res.size(); i++) {
      |                     ~~^~~~~~~~~~~~
In file included from /usr/include/c++/10/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:33,
                 from longesttrip.cpp:1:
longesttrip.cpp:43:23: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   43 |     assert(res.size() == N);
      |            ~~~~~~~~~~~^~~~
longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:146:1: warning: control reaches end of non-void function [-Wreturn-type]
  146 | }
      | ^

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 30 / 60