Submission #1255570

#	Time	Username	Problem	Language	Result	Execution time	Memory
1255570		Iskachun	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	1138 ms	1020924 KiB

tracks

//{
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <numeric>
#include <unordered_map>
//}
using namespace std;
typedef long long ll;
vector<string> a;
vector<vector<int>> comp;
int n, m, curr;
vector<int> dx = {1, -1, 0, 0}, dy = {0, 0, 1, -1};
void dfs1 (int x, int y, char c) {
    comp[x][y] = curr;
    for (int d = 0; d < 4; d++) {
        int nx = x + dx[d], ny = y + dy[d];
        if (nx < 0 or ny < 0 or nx >= n or ny >= m) continue;
        if (comp[nx][ny] or a[nx][ny] != c) continue;
        dfs1(nx, ny, c);
    }
}
vector<vector<int>> g;
vector<int> vis;
int ans;
void dfs2 (int v, int cnt = 1) {
    vis[v] = 1;
    ans = max(ans, cnt);
    for (int u : g[v]) {
        if (vis[u]) continue;
        dfs2(u, cnt + 1);
    }
}
void solve () {
    cin >> n >> m;
    a.resize(n);
    comp = vector<vector<int>> (n, vector<int> (m));
    for (auto &x : a) cin >> x;
    for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) {
        if (comp[i][j] or a[i][j] == '.') continue;
        curr++;
        dfs1(i, j, a[i][j]);
    }
    /*for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) cout << comp[i][j] << ' ';
        cout << '\n';
    }*/
    g.resize(curr + 1);
    for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) {
        if (i and comp[i - 1][j] and comp[i][j] and comp[i - 1][j] != comp[i][j]) {
            g[comp[i - 1][j]].push_back(comp[i][j]);
            g[comp[i][j]].push_back(comp[i - 1][j]);
        }
        if (j and comp[i][j - 1] and comp[i][j] and comp[i][j - 1] != comp[i][j]) {
            g[comp[i][j - 1]].push_back(comp[i][j]);
            g[comp[i][j]].push_back(comp[i][j - 1]);
        }
    }
    ans = 0;
    vector<int> dis(curr + 1, 1e9);
    dis[1] = 1;
    priority_queue<pair<int,int>> q;
    q.push({-1, 1});
    while (q.size()) {
        auto [d, v] = q.top(); q.pop();
        if (-d != dis[v]) continue;
        for (int u : g[v]) {
            if (dis[u] <= dis[v] + 1) continue;
            dis[u] = dis[v] + 1;
            q.push({-dis[u], u});
        }
    }
    int ans = 1;
    for (int x : dis) {
        if (x == 1e9) continue;
        ans = max(ans, x);
    }
    cout << ans;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int t = 1; //cin >> t;
    while (t--) solve();
}

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