Submission #730031

#	Time	Username	Problem	Language	Result	Execution time	Memory
730031		roadster	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	600 ms	138816 KiB

tracks

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;

#define pb push_back
#define sz(x) (int)(x).size()
#define f first
#define s second
#define mp make_pair


const int INF = INT_MAX;
const int MOD = 1e9 + 7;
const int hmx = 4005, wmx = 4005;
int h, w, ans = 1;
vector<string> grid(hmx);
vector<vi> depth(hmx, vi (wmx));
int dx[]{0, 1, 0, -1}, dy[]{1, 0, -1, 0};

bool is_valid(int r, int c) {
    return r >= 0 && r < h && c >= 0 && c < w && grid[r][c] != '.';
}

int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    
    cin >> h >> w;
    for (int i = 0; i < h; i++)
            cin >> grid[i];

    deque<pair<int, int>> dq;
    dq.push_front({0, 0});
    depth[0][0] = 1;

    while (!dq.empty()) {
        auto nxt = dq.front();
        dq.pop_front();
        ans = max(ans, depth[nxt.f][nxt.s]);
        for (int i = 0; i < 4; i++) {
            int x = nxt.f + dx[i], y = nxt.s + dy[i];
            if (is_valid(x, y) && depth[x][y] == 0) {
                if (grid[x][y] == grid[nxt.f][nxt.s]) {
                    depth[x][y] = depth[nxt.f][nxt.s];
                    dq.push_front({x, y});
                } else {
                    depth[x][y] = depth[nxt.f][nxt.s] + 1;
                    dq.push_back({x, y});
                }
            }
        }
    }

    cout << ans << "\n";

    return 0;
}

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