Submission #1150730

#	Time	Username	Problem	Language	Result	Execution time	Memory
1150730		gapplebee	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	750 ms	119096 KiB

tracks

#include <bits/stdc++.h>

using namespace std;

int drow[4] = {0, 1, 0, -1};
int dcol[4] = {1, 0, -1, 0};

const int MAX_W = 4000;
int depth[MAX_W][MAX_W]; // 0-indexed
char snow[MAX_W][MAX_W]; // 0-indexed

int h, w;

bool check(int row, int col)
{
    return row >= 0 && row < h && col >= 0 && col < w && !depth[row][col] && snow[row][col] != '.';
}

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

    cin >> h >> w;

    for (int i = 0; i < h; ++i)
    {
        for (int j = 0; j < w; ++j)
        {
            cin >> snow[i][j];
        }
    }

    int min_tracks = 1;
    deque<int> deq = {0, 0};
    depth[0][0] = 1;
    while (deq.size())
    {
        int row = deq.front();
        deq.pop_front();

        int col = deq.front();
        deq.pop_front();

        for (int i = 0; i < 4; ++i)
        {
            int new_row = row + drow[i];
            int new_col = col + dcol[i];
            if (check(new_row, new_col))
            {
                if (snow[row][col] == snow[new_row][new_col])
                {
                    depth[new_row][new_col] = depth[row][col];
                    deq.push_front(new_col);
                    deq.push_front(new_row);
                }
                else
                {
                    depth[new_row][new_col] = depth[row][col] + 1;
                    min_tracks = max(min_tracks, depth[new_row][new_col]);
                    deq.push_back(new_row);
                    deq.push_back(new_col);
                }
            }
        }
    }

    cout << min_tracks << '\n';
}

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