Submission #1005016

#	Time	Username	Problem	Language	Result	Execution time	Memory
1005016		roadster	Tracks in the Snow (BOI13_tracks)	C++17	65.42 / 100	485 ms	138844 KiB

tracks

#include <bits/stdc++.h>
using namespace std;

using vi = vector<int>;
using vvi = vector<vector<int> >;
using pi = pair<int, int>;
using ll = long long;

#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define f first
#define s second
#define pb push_back

#define MOD 1e9 + 7
int h, w, ans = 1;
vector<string> snow(4000);
int dx[4] {1, -1, 0, 0}, dy[4] {0, 0, 1, -1};
vvi dist(4000, vi (4000));

bool isInside(int x, int y) {
    return x >= 0 && x < h && y >= 0 && y < h && snow[x][y] != '.';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> h >> w;
    for (int i = 0; i < h; i++) cin >> snow[i];
    
    deque<pi> dq;
    dq.push_front({0, 0});
    dist[0][0] = 1;
    
    while (!dq.empty()) {
        auto curr = dq.front();
        dq.pop_front();
        ans = max(ans, dist[curr.f][curr.s]);
        
        for (int i = 0; i < 4; i++) {
            int x = curr.f + dx[i], y = curr.s + dy[i];
            if (isInside(x, y) && dist[x][y] == 0) {
                if (snow[x][y] == snow[curr.f][curr.s]) {
                    dist[x][y] = dist[curr.f][curr.s];
                    dq.push_front({x, y});
                } else {
                    dist[x][y] = dist[curr.f][curr.s] + 1;
                    dq.push_back({x, y});
                }
            }
        }
    }
    
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 21.666666666666668 / 30
• Subtask 2: 43.75 / 70