Submission #367303

#	Time	Username	Problem	Language	Result	Execution time	Memory
367303		PurpleCrayon	Stations (IOI20_stations)	C++17	5 / 100	1123 ms	1236 KiB

stations

#include "stations.h"
#include <bits/stdc++.h>
using namespace std;

#define sz(v) int(v.size())

int tt;
vector<int> ans;
vector<vector<int>> adj;

void dfs(int c=0, int p=-1, bool b=0){
    if (!b) ans[c] = tt++;
    for (auto nxt : adj[c]) if (nxt != p) dfs(nxt, c, b^1);
    if (b) ans[c] = tt++;
}
vector<int> label(int n, int k, vector<int> u, vector<int> v) {
    ans.assign(n, -1), adj.assign(n, vector<int>()), tt=0;
    for (int i = 0; i < n-1; i++) 
        adj[u[i]].push_back(v[i]), adj[v[i]].push_back(u[i]);
    dfs();
    return ans;
}

int find_next_station(int s, int t, vector<int> c) {
    if (s == 0){ //ans for the root
        for (auto nxt : c) if (nxt >= t) return nxt;
        assert(false);
    }
    bool b=s>c[0];

    if (b){ //i'm postorder
        int p = c[0];
        if (sz(c) == 1 || t < c[1] || t > s)
            return p; 
        
        int ans=-1;
        for (auto nxt : c) if (nxt != p) {
            if (nxt <= t) ans = nxt;
        }
        assert(ans != -1);
        return ans;

    } else { //i'm preorder
        int p = c[sz(c)-1];
        if (sz(c) == 1 || t < s || t >= c[sz(c)-1]) 
            return p;

        int ans=-1;
        for (auto nxt : c) if (nxt != p) {
            if (nxt >= t){
                return nxt;
            }
        }
        assert(false);
    }
}

Compilation message (stderr)

stations.cpp: In function 'int find_next_station(int, int, std::vector<int>)':
stations.cpp:48:13: warning: unused variable 'ans' [-Wunused-variable]
   48 |         int ans=-1;
      |             ^~~

• Subtask 1: 5 / 5
• Subtask 2: 0 / 8
• Subtask 3: 0 / 16
• Subtask 4: 0 / 10
• Subtask 5: 0 / 61