Submission #249472

#	Time	Username	Problem	Language	Result	Execution time	Memory
249472		AMO5	Jakarta Skyscrapers (APIO15_skyscraper)	C++17	100 / 100	380 ms	20464 KiB

skyscraper

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define eb emplace_back
#define mt make_tuple
#define all(x) (x).begin(), (x).end() 
#define sz(x) int(x.size()) 
#define MOD 1000000007

typedef long long ll;
typedef pair <int, int> ii;
typedef pair <ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef long double ld;

const ll INF=LLONG_MAX;
const int mxn=3e5+5;
bool DEBUG=0;
int n,m,start,target;
set<int>jumps[mxn];

void solve(){
	priority_queue<ii,vector<ii>,greater<ii>>pq;
	pq.push({0,start});
	vi dist(n,INT_MAX);
	while(!pq.empty()){
		ii now = pq.top();
		pq.pop();
		int cost = now.fi;
		int pos = now.se;
		if(cost>dist[pos])continue;
		dist[pos]=cost;
		if(pos==target){
			cout << cost << endl;
			return;
		}
		//to the left
		for(int jmp:jumps[pos]){
			for(int cnt=1,cur=pos-jmp; cur>=0; cur-=jmp,cnt++){
				if(dist[cur]>dist[pos]+cnt){
					dist[cur]=dist[pos]+cnt;
					pq.push({dist[cur],cur});
					if(jumps[cur].count(jmp))break;
				}
			}
		}
		// to the right
		for(int jmp:jumps[pos]){
			for(int cnt=1,cur=pos+jmp; cur<n; cur+=jmp,cnt++){
				if(dist[cur]>dist[pos]+cnt){
					dist[cur]=dist[pos]+cnt;
					pq.push({dist[cur],cur});
					if(jumps[cur].count(jmp))break;
				}
			}
		}
	}
	cout << -1 << endl;
	return;
}

int main()
{
    if(!DEBUG){ios_base::sync_with_stdio(0); cin.tie(0);}
    //freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
	cin >> n >> m;
	for(int i=0; i<m; i++){
		int pos, jmp;
		cin >> pos >> jmp;
		jumps[pos].insert(jmp);
		if(i==0)start=pos;
		if(i==1)target=pos;
	}
	solve();
}
	
// READ & UNDERSTAND
// ll, int overflow, array bounds, memset(0)
// special cases (n=1?), n+1 (1-index)
// do smth instead of nothing & stay organized
// WRITE STUFF DOWN

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