Submission #335840

#	Time	Username	Problem	Language	Result	Execution time	Memory
335840		aanastasov	Stations (IOI20_stations)	C++17	100 / 100	988 ms	1208 KiB

stations

#include "stations.h"
#include <algorithm>
#include <cassert>
//#include <iostream>
#include <vector>

void dfs(int src, int parent, int depth, std::vector<std::vector<int>>& adj,
        int& nextLabel, std::vector<int>& labels) {
    if (depth % 2 == 0) {
        labels[src] = nextLabel++;
    }
    for (int dst : adj[src]) {
        if (dst == parent) continue;
        dfs(dst, src, depth + 1, adj, nextLabel, labels);
    }
    if (depth % 2 == 1) {
        labels[src] = nextLabel++;
    }
}

std::vector<int> label(int n, int k, std::vector<int> u, std::vector<int> v) {
    assert(n <= k);
    auto adj = std::vector<std::vector<int>>(n, std::vector<int>());
    assert(u.size() == v.size());
    for (int index = 0; index < u.size(); ++index) {
        adj[u[index]].push_back(v[index]);
        adj[v[index]].push_back(u[index]);
    }
    auto labels = std::vector<int>(n, -1);
    int nextLabel = 0;
    dfs(0, -1, 0, adj, nextLabel, labels);
//    for (auto &x : labels) std::cout << x << ", "; std::cout << std::endl;
    return labels;
}

int find_next_station(int s, int t, std::vector<int> c) {
    if (s == t) return t;
    for (int neighbour : c) if (neighbour == t) return t;
    std::sort(c.begin(), c.end());
    auto rc = std::vector<int>(c.begin(), c.end());
    std::reverse(rc.begin(), rc.end());
    if (s == 0) { // we are at the root => there's no parent node
        for (int neighbour : c) if (t <= neighbour) return neighbour;
    } else {
        if (s < c[0]) { // even depth
            if (t > s && t < c.back()) { // go to a child
                for (int neighbour : c) if (t <= neighbour) return neighbour;
            } else { // go to parent
                return c.back();
            }
        } else { // odd depth
            assert(c.back() < s);
            if (t > c[0] && t < s) { // go to a child
                for (int neighbour : rc) if (t >= neighbour) return neighbour;
            } else { // go to parent
                return c[0];
            }
        }
    }
    assert(false);
}

Compilation message (stderr)

stations.cpp: In function 'std::vector<int> label(int, int, std::vector<int>, std::vector<int>)':
stations.cpp:25:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   25 |     for (int index = 0; index < u.size(); ++index) {
      |                         ~~~~~~^~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 16 / 16
• Subtask 4: 10 / 10
• Subtask 5: 61 / 61