Submission #771220

#	Time	Username	Problem	Language	Result	Execution time	Memory
771220		synthesis	Tracks in the Snow (BOI13_tracks)	C++17	91.25 / 100	2089 ms	708496 KiB

tracks

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define fi first
#define se second
#define pii pair<int, int>
#define pb push_back
#define vi vector<int>
#define all(x) x.begin(), x.end()

using namespace std;
using namespace __gnu_pbds;
using ll = long long int;
using ull = unsigned long long int;

constexpr ll mod = 1e9 + 7;
constexpr ll INF = LONG_LONG_MAX;

int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
string moves = "URDL";

int main()
{
    //tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> q;
    /*freopen("problemname.in", "r", stdin);
    freopen("problemname.out", "w", stdout);*/
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, m;
    cin >> n >> m;
    char a[n][m];
    for(int i = 0;i<n;++i) {
        for(int j = 0;j<m;++j) {
            cin >> a[i][j];
        }
    }
    bool vis[n][m];
    int cc[n][m], c = 0;
    memset(cc, 0, sizeof cc);
    memset(vis, false, sizeof vis);
    for(int i = 0;i<n;++i) {
        for(int j = 0;j<m;++j) {
            if (!vis[i][j] && a[i][j] != '.') {
                queue<pii> q;
                q.push({i, j});
                ++c;
                vis[i][j] = true;
                cc[i][j] = c;
                while(!q.empty()) {
                    pii node = q.front();
                    q.pop(); 
                    for(int k = 0;k<4;++k) {
                        int nx = node.fi + dx[k], ny = node.se + dy[k];
                        if (nx >= 0 && ny >= 0 && nx < n && ny < m) {
                            if (a[nx][ny] == a[i][j] && !vis[nx][ny]) {
                                q.push({nx, ny});
                                vis[nx][ny] = true;
                                cc[nx][ny] = c;
                            }
                        }
                    }
                }
            }
        }
    }
    memset(vis, false, sizeof vis);
    set<int> adj[c + 1];
    int d[c + 1];
    for(int i = 0;i<n;++i) {
        for(int j = 0;j<m;++j) {
            if (!vis[i][j] && a[i][j] != '.') {
                queue<pii> q;
                q.push({i, j});
                vis[i][j] = true;
                while(!q.empty()) {
                    pii node = q.front();
                    q.pop(); 
                    for(int k = 0;k<4;++k) {
                        int nx = node.fi + dx[k], ny = node.se + dy[k];
                        if (nx >= 0 && ny >= 0 && nx < n && ny < m) {
                            if (a[nx][ny] == a[i][j] && !vis[nx][ny]) {
                                q.push({nx, ny});
                                vis[nx][ny] = true;
                            }
                            if (cc[nx][ny] != cc[i][j] && cc[nx][ny] != 0) {
                                adj[cc[i][j]].insert(cc[nx][ny]);
                                adj[cc[nx][ny]].insert(cc[i][j]);
                            }
                        }
                    }
                }
            }
        }
    }
    queue<int> q;
    q.push(cc[0][0]);
    bool ok[c + 1];
    memset(ok, false, sizeof ok);
    ok[cc[0][0]] = true;
    d[cc[0][0]] = 0;
    int ans = 0;
    while(!q.empty()) {
        int node = q.front();
        q.pop();
        for(const int& v:adj[node]) {
            if (!ok[v]) {
                q.push(v);
                ok[v] = true;
                d[v] = d[node] + 1;
                ans = max(ans, d[v]);
            }
        }
    }
    cout << ans + 1 << endl;
    return 0;
}

• Subtask 1: 30 / 30
• Subtask 2: 61.25 / 70