Submission #1279926

#	Time	Username	Problem	Language	Result	Execution time	Memory
1279926		ducanh0811	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	513 ms	126932 KiB

tracks

#include <bits/stdc++.h>
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define REV(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
using namespace std;

int n, m;
#define MAXN 4005
char a[MAXN][MAXN];

const int dx[] = {0, 1, 0, -1};
const int dy[] = {-1, 0, 1, 0};

int dist[MAXN][MAXN];

bool valid(int i, int j){
    return (i >= 1 && i <= n && j >= 1 && j <= m);
}

void solve(){
    cin >> n >> m;
    FOR(i, 1, n){
        FOR(j, 1, m){
            cin >> a[i][j];
        }
    }
    deque<pair<int, int>> dq;
    memset(dist, -1, sizeof dist);
    dist[1][1] = 1;
    dq.push_back({1, 1});
    while (dq.size()){
        int i, j; tie(i, j) = dq.front();
        dq.pop_front();
        FOR(k, 0, 3){
            int ii = i + dy[k];
            int jj = j + dx[k];
            if (valid(ii, jj) && dist[ii][jj] == -1 && a[ii][jj] != '.'){
                int w = (a[ii][jj] != a[i][j]);
                dist[ii][jj] = dist[i][j] + w;
                if (w == 0) dq.push_front({ii, jj});
                    else dq.push_back({ii, jj});
            }
        }
    }
    int res = 0;
    FOR(i, 1, n) FOR(j, 1, m) res = max(res, dist[i][j]);
    cout << res;
}

#define task "test"
int32_t main(){
    if (fopen(task".inp","r")){
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    solve();
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'int32_t main()':
tracks.cpp:52:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:53:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   53 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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