Submission #970000

#	Time	Username	Problem	Language	Result	Execution time	Memory
970000		Ghetto	Race (IOI11_race)	C++17	Compilation error	0 ms	0 KiB

race

#include <bits/stdc++.h>
using namespace std;
using lint = long long;
using pil = pair<int, lint>;
using pli = pair<lint, int>;
using mli = unordered_map<lint, int>;
const int MAX_N = 2e5 + 5, INF = 2e9;

int n;
lint k;
vector<pil> adj[MAX_N];

bool del[MAX_N];
int sub_size[MAX_N];
void upd_sizes(int u, int par = -1) {
    sub_size[u] = 1;
    for (pil x : adj[u]) {
        int v = x.first;
        if (v == par || del[v]) continue;
        upd_sizes(v, u);
        sub_size[u] += sub_size[v];
    }
}
int find_cent(int u, int tot_size, int par = -1) {
    for (pil x : adj[u]) {
        int v = x.first;
        if (v == par || del[v]) continue;
        if (sub_size[v] * 2 > tot_size) return find_cent(v, tot_size, u);
    }
    return u;
}
mli lens[MAX_N], pref_lens;
void merge(mli& x, mli& y) { // y into x
    if (x.size() < y.size()) x.swap(y);
    for (pli z : y) 
        x[z.first] = x.count(z.first) ? min(x[z.first], z.second) : z.second;
}
void upd_lens(int u, int par, lint dist, int depth = 1) {
    lens[u].insert({dist, depth});
    for (pil x : adj[u]) {
        int v = x.first;
        if (v == par || del[v]) continue;
        upd_lens(v, u, dist + x.second, depth + 1);
        merge(lens[u], lens[v]);
    }
}
int ans = INF;
void build(int u) {
    upd_sizes(u);
    int cent = find_cent(u, sub_size[u]);
    pref_lens.clear();
    for (pil x : adj[cent]) if (!del[x.first]) lens[x.first].clear();
    for (pil x : adj[cent]) {
        int v = x.first;
        if (del[v]) continue;
        upd_lens(v, cent, x.second);
        for (pli y : lens[v]) {
            if (y.first == k) ans = min(ans, y.second);
            else if (pref_lens.count(k - y.first)) ans = min(ans, y.second + pref_lens[k - y.first]);
        }
        merge(pref_lens, lens[v]);
    }

    del[cent] = true;
    for (pil x : adj[cent]) 
        if (!del[x.first]) build(x.first);
}

int main() {
    freopen("race.in", "r", stdin);
    freopen("race.out", "w", stdout);

    cin.sync_with_stdio(false); cin.tie(0);

    cin >> n >> k;
    for (int i = 1; i < n; i++) {
        int u, v; cin >> u >> v;
        lint w; cin >> w;
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
    }

    build(0);
    if (ans == INF) ans = -1;
    cout << ans << '\n';
}

Compilation message (stderr)

race.cpp: In function 'int main()':
race.cpp:70:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |     freopen("race.in", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
race.cpp:71:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |     freopen("race.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/ccudlUH8.o: in function `main':
race.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccKbOYV5.o:grader.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccKbOYV5.o: in function `main':
grader.cpp:(.text.startup+0x28): undefined reference to `best_path(int, int, int (*) [2], int*)'
collect2: error: ld returned 1 exit status