Submission #892870

#	Time	Username	Problem	Language	Result	Execution time	Memory
892870		eysbutno	Crocodile's Underground City (IOI11_crocodile)	C++17	Compilation error	0 ms	0 KiB

crocodile

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
#define pb push_back
#define ins insert
#define f first 
#define s second 

const int MX = 1e5;
const ll INF = 1e18;
vector<pii> adj[MX];
ll dist[MX], fin[MX];
int main() {
    cin.tie(0) -> sync_with_stdio(0);
    int n, m, k; cin >> n >> m >> k;
    for (int i = 0; i < m; i++) {
        int x, y, w; 
        cin >> x >> y >> w;
        adj[x].pb({y, w});
        adj[y].pb({x, w});
    }
    for (int i = 0; i < n; i++) {
        dist[i] = INF, fin[i] = INF;
    }
    vector<int> st(k);
    priority_queue<pll> pq;
    for (int i = 0; i < k; i++) {
        int x; cin >> x;
        pq.push({0, x});
        st[i] = x;
        dist[x] = 0;
    }
    while (!pq.empty()) {
        auto N = pq.top(); pq.pop();
        ll t = -N.f, u = N.s;
        if (dist[u] != t) continue;
        for (auto [v, w] : adj[u]) {
            if (dist[u] + w < dist[v]) {
                dist[v] = dist[u] + w;
                pq.push({-dist[v], v});
            }
        }
    }
    fin[0] = 0;
    pq.push({0, 0});
    while (!pq.empty()) {
        auto N = pq.top(); pq.pop();
        ll t = -N.f, u = N.s;
        if (fin[u] != t) continue;
        vector<vector<ll>> pos;
        for (auto [v, w] : adj[u]) {
            pos.pb({w + dist[v], v, w});
        }
        sort(all(pos), [&](auto& x, auto& y) {
            return x[0] < y[0];
        });
        for (int i = 1; i < sz(pos); i++) {
            ll v = pos[i][1], w = pos[i][2];
            if (t + w < fin[v]) {
                fin[v] = t + w;
                pq.push({-fin[v], v});
            }
        }
    }
    ll res = 2e9;
    for (int i : st) {
        smin(res, fin[i]);
    }
    cout << res << '\n';
}
/**
 * Problem: IOI, Crocodile.
 * Observations:
 * 1. You will never try to go
 * backwards, because there's no 
 * point to doing that.
 * 2. Because of observation 1,
 * each possible decision must have
 * an alternative that doesn't 
 * go backwards.
 * 
 * Algorithm:
 * First, calculate shortest paths.
 * You can never pick the #1 option,
 * so always pick the #2 option in terms
 * of the distance.
 * 
 * Note: IDK if multi-source Dijkstra
 * works, but it should work. IDK.
*/

Compilation message (stderr)

/usr/bin/ld: /tmp/ccMkHlFN.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccFNFgZJ.o:crocodile.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccMkHlFN.o: in function `main':
grader.cpp:(.text.startup+0x36): undefined reference to `travel_plan(int, int, int (*) [2], int*, int, int*)'
collect2: error: ld returned 1 exit status