Submission #491788

#	Time	Username	Problem	Language	Result	Execution time	Memory
491788		Victor	Tracks in the Snow (BOI13_tracks)	C++17	97.81 / 100	801 ms	1048580 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, num_marked = 0, ans = 0;
char cur_animal;
vii next_vis;

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

void dfs(int row, int col) {
    visited[row][col] = taken[row][col] = 1;
    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) dfs(nr, nc);
            if (!taken[nr][nc] && grid[nr][nc] != cur_animal&&grid[nr][nc]!='.') {
                taken[nr][nc] = 1;
                next_vis.emplace_back(nr, nc);
            }
        }
    }
}

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

    cin >> rows >> cols;

    assert(1<=rows&&rows<=4000);
    assert(1<=cols&&cols<=4000);
    rep(i, 0, rows) {
        cin >> grid[i];
        trav(cell, grid[i]) if (cell != '.')++ num_marked;
    }

    cur_animal = grid[0][0];
    vii cur_vis;
    cur_vis.emplace_back(0, 0);

    while (!cur_vis.empty()) {
        trav(item, cur_vis) {
            int row, col;
            tie(row, col) = item;
            if(!visited[row][col])dfs(row,col);
        }

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

        cur_vis.swap(next_vis);
        next_vis.clear();
        ++ans;
    }

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

• Subtask 1: 30 / 30
• Subtask 2: 67.8125 / 70