Submission #682021

#	Time	Username	Problem	Language	Result	Execution time	Memory
682021		junkbot	Stations (IOI20_stations)	C++14	100 / 100	884 ms	1356 KiB

stations

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

using namespace std;

#define D(x...) fprintf(stderr, x)
#define D(x...)

const int MAX_N = 1005;
const int UNLABELLED = -1;
const int PENDING = -2;

struct Solve {
    int upto;
    vector<vector<int>> adjlist;
    vector<int> labels;

    Solve(int n, vector<int> u, vector<int> v) : upto(0), adjlist(n), labels(n) {
        for (auto i=0;i<u.size();i++) {
            adjlist[u[i]].push_back(v[i]);
            adjlist[v[i]].push_back(u[i]);
        }
        fill(labels.begin(), labels.end(), UNLABELLED);
    }

    // label everything in u's subtree.
    void go(int u, bool isPre) {
        if (labels[u] != UNLABELLED) return;
        labels[u] = PENDING;

        if (isPre) labels[u] = getNext();
        for (auto v: adjlist[u]) go(v, !isPre);
        if (!isPre) labels[u] = getNext();
    }

    int getNext() {
        int ret = upto;
        upto++;
        return ret;
    }
};

std::vector<int> label(int n, int k, std::vector<int> u, std::vector<int> v) {
    auto solver = new Solve(n, u, v);
    solver->go(0, true);

    vector<int> ret;
    for (auto l: solver->labels) {
        ret.push_back(l);
    }
    D("labels:");
    for (auto l: solver->labels) {
        D(" %d", l);
    }
    D("\n");

	return ret;
}

int find_next_station(int s, int t, std::vector<int> c) {
    if (s < c.front()) {
        // preorder
        int left_exclusive = s;
        for (auto i=0;i<c.size()-1;i++) {
            auto l = c[i];
            if (left_exclusive < t && t <= l) return l;
            left_exclusive = l;
        }
        return c.back();
    } else {
        // postorder
        int right_exclusive = s;
        for (auto i=c.size()-1;i>0;i--) {
            auto l = c[i];
            if (l <= t && t < right_exclusive) return l;
            right_exclusive = l;
        }
        return c.front();
    }
}

Compilation message (stderr)

stations.cpp:7: warning: "D" redefined
    7 | #define D(x...)
      | 
stations.cpp:6: note: this is the location of the previous definition
    6 | #define D(x...) fprintf(stderr, x)
      | 
stations.cpp: In constructor 'Solve::Solve(int, std::vector<int>, std::vector<int>)':
stations.cpp:19:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   19 |         for (auto i=0;i<u.size();i++) {
      |                       ~^~~~~~~~~
stations.cpp: In function 'std::vector<int> label(int, int, std::vector<int>, std::vector<int>)':
stations.cpp:52:15: warning: unused variable 'l' [-Wunused-variable]
   52 |     for (auto l: solver->labels) {
      |               ^
stations.cpp: In function 'int find_next_station(int, int, std::vector<int>)':
stations.cpp:64:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |         for (auto i=0;i<c.size()-1;i++) {
      |                       ~^~~~~~~~~~~

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