Submission #564908

#	Time	Username	Problem	Language	Result	Execution time	Memory
564908		training4usaco	Jakarta Skyscrapers (APIO15_skyscraper)	C++11	100 / 100	221 ms	8616 KiB

skyscraper

#include <iostream>
#include <vector>
#include <queue>
#include <set>
#include <algorithm>
 
using namespace std;
 
#define MAXN 30005
#define INF 1000000009

#define pii pair<int, int>
#define mp make_pair
#define f first
#define s second

int n, m;
int b[MAXN];
int p[MAXN];
int dist[MAXN];
set<int> jumpsset[MAXN];
vector<int> jumps[MAXN];
 
void solve(int s) {
    dist[b[0]] = 0;
    priority_queue<pii, vector<pii>, greater<pii>> pq;

    pq.push(mp(0,b[0]));
    
    while (!pq.empty()) {
        pii node = pq.top();
        pq.pop();

        if (node.f > dist[node.s]) {
            continue;
        }

        for(auto jump : jumps[node.s]) {
            for (int j = 1; node.s + jump * j < n; ++j) {   // forward
                if (dist[node.s + jump * j] > node.f + j) {
                    dist[node.s + jump * j] = node.f + j;

                    pq.push(mp(node.f + j, node.s + jump * j));

                    if (binary_search(jumps[node.s + jump * j].begin(), jumps[node.s + jump * j].end(), jump)) {    // no need to have multiple doges going same "route"
                        break;
                    }
                }
            }
            for (int j = 1; node.s - jump * j >= 0;++j) {    // backward
                if (dist[node.s - jump * j] > node.f + j) {
                    dist[node.s - jump * j] = node.f + j;
                    pq.push(mp(node.f + j, node.s - jump * j));
                    if (binary_search(jumps[node.s - jump * j].begin(), jumps[node.s - jump * j].end(), jump)) {
                        break;
                    }
                }
            }
        }
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n >> m;
    for(int i = 0; i < m; ++i) {
        cin >> b[i] >> p[i];
        jumpsset[b[i]].insert(p[i]);
    }
    for(int i = 0; i < n; ++i) {
        for(auto jump : jumpsset[i]) {
            jumps[i].push_back(jump);
        }
    }

    for(int i = 0; i <= n; ++i) {
        dist[i] = INF;
    }

    solve(b[0]);

    if (dist[b[1]] == INF) {
        cout << "-1" << endl;
        return 0;
    }
    cout << dist[b[1]] << endl;
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 14 / 14
• Subtask 4: 21 / 21
• Subtask 5: 43 / 43