Submission #598682

#	Time	Username	Problem	Language	Result	Execution time	Memory
598682		stevancv	Tracks in the Snow (BOI13_tracks)	C++14	5.52 / 100	1203 ms	1048576 KiB

tracks

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 4e3 + 2;
int a[N][N], c[N][N], n, m, iden;
bool Can(int x, int y) {return 0 <= x && x < n && 0 <= y && y < m && c[x][y] == -1;}
void Dfs(int i, int j) {
    c[i][j] = iden;
    if (Can(i - 1, j) && a[i - 1][j] == a[i][j]) Dfs(i - 1, j);
    if (Can(i, j - 1) && a[i][j - 1] == a[i][j]) Dfs(i, j - 1);
    if (Can(i + 1, j) && a[i + 1][j] == a[i][j]) Dfs(i + 1, j);
    if (Can(i, j + 1) && a[i][j + 1] == a[i][j]) Dfs(i, j + 1);
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for (int i = 0; i < n; i++) {
        string s; cin >> s;
        for (int j = 0; j < m; j++) {
            c[i][j] = -1;
            if (s[j] == 'F') a[i][j] = 1;
            if (s[j] == 'R') a[i][j] = 2;
        }
    }
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (c[i][j] == -1 && a[i][j] > 0) {
                Dfs(i, j);
                iden += 1;
            }
        }
    }
    vector<set<int>> g(iden);
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (c[i][j] == -1) continue;
            if (i < n - 1 && c[i + 1][j] != c[i][j] && c[i + 1][j] != -1) g[c[i][j]].insert(c[i + 1][j]);
            if (j < m - 1 && c[i][j + 1] != c[i][j] && c[i][j + 1] != -1) g[c[i][j]].insert(c[i][j + 1]);
        }
    }
    assert(c[0][0] == c[n - 1][m - 1]);
    vector<int> dist(iden, 1e9);
    queue<int> q;
    dist[0] = 0;
    q.push(0);
    while (!q.empty()) {
        int s = q.front(); q.pop();
        for (int u : g[s]) {
            if (dist[u] > dist[s] + 1) {
                dist[u] = dist[s] + 1;
                q.push(u);
            }
        }
    }
    int ans = 0;
    for (int i = 0; i < iden; i++) {
        smax(ans, dist[i] + 1);
    }
    cout << ans << en;
    return 0;
}

• Subtask 1: 3.3333333333333335 / 30
• Subtask 2: 2.1875 / 70