Submission #979783

#TimeUsernameProblemLanguageResultExecution timeMemory
979783VMaksimoski008Jakarta Skyscrapers (APIO15_skyscraper)C++17
100 / 100
103 ms6840 KiB
#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;

const int maxn = 3e4 + 5;
vector<int> mp[maxn+1], B(maxn+1), P(maxn+1), dist(maxn+1, 1e9);
set<int> seen[maxn+1];

int main() {
    int n, m;
    cin >> n >> m;

    for(int i=0; i<m; i++) {
        cin >> B[i] >> P[i];
        if(!seen[++B[i]].count(P[i])) mp[B[i]].push_back(P[i]);
        seen[B[i]].insert(P[i]);
    }

    priority_queue<pii, vector<pii>, greater<pii> > pq;

    dist[B[0]] = 0;
    pq.push({ 0, B[0] });

    while(!pq.empty()) {
        auto [d, u] = pq.top();
        pq.pop();

        if(d != dist[u]) continue;
       
        for(int &j : mp[u]) {
            int v = u + j;
            while(v <= n) {
                if(dist[v] > d + (v - u) / j) {
                    dist[v] = d + (v - u) / j;
                    pq.push({ dist[v], v });
                }
                if(seen[v].count(j)) break;
                v += j;
            }

            v = u - j;
            while(v >= 1) {
                if(dist[v] > d + (u - v) / j) {
                    dist[v] = d + (u - v) / j;
                    pq.push({ dist[v], v });
                }
                if(seen[v].count(j)) break;
                v -= j;
            }
        }
    }

    cout << (dist[B[1]] == 1e9 ? -1 : dist[B[1]]) << '\n';
    return 0;
}
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