Submission #781009

#	Time	Username	Problem	Language	Result	Execution time	Memory
781009		Josia	Stations (IOI20_stations)	C++17	100 / 100	749 ms	824 KiB

stations

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

using namespace std;




vector<int> pre;
vector<int> post;
vector<vector<int>> graph;
vector<int> depth;

int tim;
void dfs(int v, int d) {
	if (pre[v] != -1) return;
	pre[v] = tim++;
	depth[v] = d;
	for (int i: graph[v]) {
		dfs(i, d+1);
	}
	post[v] = tim++;
}


vector<int> label(int n, int k, vector<int> u, vector<int> v) {
	tim = 0;
	pre.assign(n, -1);
	post.assign(n, -1);
	depth.assign(n, -1);
	graph.clear(); graph.resize(n);

	for (int i = 0; i<n-1; i++) {
		graph[u[i]].push_back(v[i]);
		graph[v[i]].push_back(u[i]);
	}

	dfs(0, 0);

	// for (int i: pre) cerr << i << " ";
	// cerr << "\n";


	vector<int> labels(n);

    int mod = labels[0]%2;

	for (int i=0; i<n; i++) {
		if (depth[i]%2) labels[i] = pre[i];
		else labels[i] = post[i];
	}


    vector<pair<int, int>> comp(n);
	for (int i=0; i<n; i++) {
		comp[i] = {labels[i], i};
	}
    sort(comp.begin(), comp.end());

    for (int i=0; i<n; i++) {
        comp[i].first = i;
        swap(comp[i].first, comp[i].second);
    }
    sort(comp.begin(), comp.end());

    for (int i = 0; i<n; i++) {
        labels[i] = comp[i].second;
    }

	return labels;
}

int find_next_station(int s, int t, vector<int> c) {

    if (c.size() == 1) return c[0];

	sort(c.begin(), c.end());

	bool bound = s > c[0];      // 0 lower; 1 higher

    if (bound == 0) {
        if (t < s) return c.back();
        if (t > *prev(c.end())) return c.back();

        for (int i = 1; i<c.size(); i++) {
            if (t > c[i-1] && t <= c[i]) return c[i];
        }

        return c[0];
    }
    else {
        if (t > s) return c[0];
        if (t < c[1]) return c[0];

        for (int i = 0; i<c.size()-1; i++) {
            if (t < c[i+1] && t >= c[i]) return c[i];
        }

        return c.back();
    }

}

Compilation message (stderr)

stations.cpp: In function 'std::vector<int> label(int, int, std::vector<int>, std::vector<int>)':
stations.cpp:46:9: warning: unused variable 'mod' [-Wunused-variable]
   46 |     int mod = labels[0]%2;
      |         ^~~
stations.cpp: In function 'int find_next_station(int, int, std::vector<int>)':
stations.cpp:85:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |         for (int i = 1; i<c.size(); i++) {
      |                         ~^~~~~~~~~
stations.cpp:95:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   95 |         for (int 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