Submission #56868

#	Time	Username	Problem	Language	Result	Execution time	Memory
56868		Benq	Jakarta Skyscrapers (APIO15_skyscraper)	C++14	100 / 100	741 ms	123684 KiB

skyscraper

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 30001;

int N,M, st, en;
bitset<MX> oc[MX], visit;
vi sky[MX];

queue<array<int,3>> q;

void tri(int x, array<int,3> y) {
    if (x < 0 || x >= N) return;
    if (oc[x][y[2]]) return;
    oc[x][y[2]] = 1;
    q.push({y[0]+1,x,y[2]});
    
    if (!visit[x]) {
        for (int i: sky[x]) q.push({y[0]+1,x,i});
        visit[x] = 1;
    }
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> N >> M;
    F0R(i,M) {
        int B,P; cin >> B >> P;
        sky[B].pb(P);
        if (i == 0) st = B;
        if (i == 1) en = B;
    }
    for (int i: sky[st]) {
        oc[st][i] = 1;
        q.push({0,st,i});
    }
    while (sz(q)) {
        auto a = q.front(); q.pop();
        if (a[1] == en) {
            cout << a[0];
            exit(0);
        }
        tri(a[1]-a[2],a);
        tri(a[1]+a[2],a);
    }
    cout << -1;
}

/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

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