Submission #927974

#	Time	Username	Problem	Language	Result	Execution time	Memory
927974		Regulus	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	732 ms	68196 KiB

tracks

#include <bits/stdc++.h>
#define IO ios::sync_with_stdio(false);cin.tie(0);
#define debug(x) cerr << #x << " = " << (x) << ' '
#define bug(x) cerr << (x) << ' '
#define endl cerr << '\n'
#define all(v) (v).begin(), (v).end()
#define SZ(v) (ll)(v).size()
#define lowbit(x) (x)&-(x)
#define pb emplace_back
#define F first
#define S second
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;

const int N = 4005;
int n, m, dx[]={-1, 0, 0, 1}, dy[]={0, -1, 1, 0};
char a[N][N];
bool vis[N][N];
queue<pll> Q, Q2;

inline bool chk(int x, int y)
{ return x >= 1 && x <= n && y >= 1 && y <= m; }

int main(void)
{ IO
    int i, ans = 0;

    cin >> n >> m;
    for (i=1; i <= n; ++i)
        for (int j=1; j <= m; ++j) cin >> a[i][j];

    if (a[1][1] != a[n][m]) assert(0);
    Q.push({1, 1}), vis[1][1] = 1;
    while (1)
    {
        ++ans;
        while (!Q.empty())
        {
            int x = Q.front().F, y = Q.front().S; Q.pop();
            for (int d=0; d < 4; ++d)
            {
                int xx = x + dx[d], yy = y + dy[d];
                if (!chk(xx, yy) || vis[xx][yy] || a[xx][yy] == '.') continue;
                vis[xx][yy] = 1;
                if (a[xx][yy] != a[x][y]) Q2.push({xx, yy});
                else Q.push({xx, yy});
            }
        }

        if (Q2.empty()) break;
        while (!Q2.empty())
            Q.push(Q2.front()), Q2.pop();
    }

    cout << ans << '\n';

    return 0;
}

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