Submission #491792

#	Time	Username	Problem	Language	Result	Execution time	Memory
491792		Victor	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	689 ms	27588 KiB

tracks

// #pragma GCC target ("avx,avx2,fma")
// #pragma GCC optimize ("Ofast,inline") // O1 - O2 - O3 - Os - Ofast
// #pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define per(i, a, b) for (int i = (b - 1); i >= (a); --i)
#define trav(a, x) for (auto &a : x)

#define all(x) x.begin(), x.end()
#define sz(x) x.size()
#define pb push_back
#define debug(x) cout << #x << " = " << x << endl

#define umap unordered_map
#define uset unordered_set

typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;

typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<pll> vpll;

const int INF = 1'000'000'007;

int dr[] = {1, -1, 0, 0};
int dc[] = {0, 0, -1, 1};

bitset<4001> visited[4001], taken[4001];
string grid[4001];
int rows, cols, ans = 0;
char cur_animal;

bool valid(int row, int col) { return 0 <= row && row < rows && 0 <= col && col < cols; }

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    cin >> rows >> cols;

    rep(i, 0, rows) cin >> grid[i];

    cur_animal = grid[0][0];
    queue<int> q;
    visited[0][0]=1;
    q.push(0);

    while (!q.empty()) {
        queue<int> nxtq;

        while (!q.empty()) {
            int pos = q.front();
            q.pop();
            int row = pos / cols, col = pos - row * cols;

            rep(i, 0, 4) {
                int nr = row + dr[i], nc = col + dc[i];
                if (valid(nr, nc)) {
                    if (!visited[nr][nc] && grid[nr][nc] == cur_animal) {
                        q.push(nr * cols + nc);
                        visited[nr][nc]=1;
                    }
                    if (!visited[nr][nc] && grid[nr][nc] != cur_animal && grid[nr][nc] != '.') {
                        visited[nr][nc] = 1;
                        nxtq.push(nr * cols + nc);
                    }
                }
            }
        }

        if (cur_animal == 'F')
            cur_animal = 'R';
        else
            cur_animal = 'F';

        q.swap(nxtq);
        ++ans;
    }

    cout << ans << endl;
    return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70