Submission #1078626

#	Time	Username	Problem	Language	Result	Execution time	Memory
1078626		Yang8on	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	506 ms	131172 KiB

tracks

#include <bits/stdc++.h>
#define Y8o "main"
#define maxn (int) 4005
#define ll long long
#define pii pair<int, int>
#define gb(i, j) ((i >> j) & 1)
#define all(x) x.begin(), x.end()
#define _left id * 2, l, mid
#define _right id * 2 + 1, mid + 1, r

#define f first
#define s second

using namespace std;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll GetRandom(ll l, ll r) {
    return uniform_int_distribution<ll> (l, r) (rng);
}
void iof() {
    if(fopen(Y8o".inp", "r"))
    {
        freopen(Y8o".inp", "r", stdin);
//        freopen(Y8o".out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(NULL), cout.tie(NULL);
}
void ctime() {
    cerr << "\n" << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
}

int m, n;
char a[maxn][maxn];
int dp[maxn][maxn];

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, -1, 1};
bool exist(int u, int v) {
    return 1 <= u && u <= m && 1 <= v && v <= n && a[u][v] != '.';
}

void bfs() {
    dp[1][1] = 1;
    deque<pii> q;
    q.push_back({ 1, 1 });

    while(q.size()) {
        int i, j; tie(i, j) = q.front();
        q.pop_front();

        for(int t = 0; t <= 3; t ++) {
            int u = i + dx[t], v = j + dy[t];
            if(exist(u, v) && dp[u][v] == 0) {
                if(a[u][v] == a[i][j]) {
                    dp[u][v] = dp[i][j];
                    q.push_front({ u, v });
                }
                else {
                    dp[u][v] = dp[i][j] + 1;
                    q.push_back({ u, v });
                }
            }
        }
    }
}
void solve() {
    cin >> m >> n ;
    for(int i = 1; i <= m; i ++) for(int j = 1; j <= n; j ++)
        cin >> a[i][j] ;

    bfs();

    int ans = 0;
    for(int i = 1; i <= m; i ++) for(int j = 1; j <= n; j ++)
        ans = max(ans, dp[i][j]);
    cout << ans;
}

int main() {
    iof();

    int nTest = 1;
//    cin >> nTest;

    while(nTest --) {
        solve();
    }

    ctime();
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'void iof()':
tracks.cpp:23:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |         freopen(Y8o".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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