Submission #1257786

#	Time	Username	Problem	Language	Result	Execution time	Memory
1257786		gohann	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	592 ms	135984 KiB

tracks

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

struct Node {
    int x, y, w;
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int H, W;
    cin >> H >> W;

    vector<string> grid(H);
    for (int i = 0; i < H; i++) cin >> grid[i];

    vector<vector<int>> dist(H, vector<int>(W, 1e9));
    const int dx[4] = {-1, 1, 0, 0};
    const int dy[4] = {0, 0, -1, 1};

    deque<Node> dq;
    dq.push_front({0, 0, 0});
    dist[0][0] = 0;

    while (!dq.empty()) {
        auto [x, y, w] = dq.front();
        dq.pop_front();

        for (int dir = 0; dir < 4; dir++) {
            int nx = x + dx[dir];
            int ny = y + dy[dir];
            if (nx < 0 || ny < 0 || nx >= H || ny >= W) continue;
            if (grid[nx][ny] == '.') continue;

            int nw = (grid[x][y] != grid[nx][ny]);
            if (dist[x][y] + nw < dist[nx][ny]) {
                dist[nx][ny] = dist[x][y] + nw;
                if (nw == 0) dq.push_front({nx, ny, nw});
                else dq.push_back({nx, ny, nw});
            }
        }
    }

    int maxi = 0;
    for (int i = 0; i < H; i++)
        for (int j = 0; j < W; j++)
            if (dist[i][j] != 1e9)
                maxi = max(maxi, dist[i][j]);

    cout << maxi + 1;
}

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