Submission #876213

#	Time	Username	Problem	Language	Result	Execution time	Memory
876213		vjudge1	Tracks in the Snow (BOI13_tracks)	C++17	91.25 / 100	803 ms	1048576 KiB

tracks

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double
#define pb push_back //emplace_back
#define pp pop_back
#define pii pair<ll, ll> //pair<int, int>
#define all(x) (x).begin(),(x).end()
#define mp(a,b) make_pair(a , b)
#define lb lower_bound
#define ub upper_bound
#define sz(x) (ll)(x).size()
#define F first
#define S second
#define bg(x) (x).begin()
#define For(x, n) for(int (x) = 0 ; (x) < (n) ; (x)++)
#define debug(x) cout << #x << " : " << x << endl
#define endl (char)(10)
#define arr(x) array<int , (x)>
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define FAST ios_base::sync_with_stdio(0);cin.tie(0);
     
ll Sum(ll a , ll b , ll MOD)
{
    a %= MOD;
    b %= MOD;
    a += b;
    return a % MOD;
}
     
ll Mul(ll a , ll b , ll MOD)
{
    a %= MOD;
    b %= MOD;
    a *= b;
    return a % MOD;
}
     
ll Pow(ll a , ll b , ll MOD)
{
    ll res = 1;
    while(b)
    {
        if((b & 1))res = Mul(res , a , MOD);
        a = Mul(a , a , MOD);
        b >>= 1;
    }
    return res;
}
     
ll Min(ll a , ll b)
{
    if(a > b)return b;
    return a;
}
     
ll Max(ll a , ll b)
{
    if(a > b)return a;
    return b;
}
     
ll Ceil(ll a , ll b)
{
    if(a % b)return (a/b)+1;
    return a/b;
}
     
/////////////////////
//VALS
const ll maxn = 4009;

ll n,m;
string s[maxn];

bool vis[maxn][maxn];
ll ans;

ll x[4] = {1,-1,0,0};
ll y[4] = {0,0,1,-1};
/////////////////////
//FUNCTIONS
void bfs(queue<pii> q1 , queue<pii> q2, ll d)
{
	if(q1.empty())return;
	ans = d;
	while(!q1.empty())
	{
		pii p = q1.front();
		q1.pop();
		
		//debug(p.F);
		//debug(p.S);

		For(i,4)
		{
			if(p.F + x[i] < 0 or p.F + x[i] >= n or p.S + y[i] < 0 or p.S + y[i] >= m or s[p.F + x[i]][p.S + y[i]] == '.' or vis[p.F + x[i]][p.S + y[i]] == 1)continue;
			
			vis[p.F + x[i]][p.S + y[i]] = 1;

			bool flag = (s[p.F + x[i]][p.S + y[i]] == s[p.F][p.S]);

			//debug(i);
			//debug(flag);

			if(flag)
				q1.push(mp(p.F + x[i], p.S + y[i]));
			else
				q2.push(mp(p.F + x[i], p.S + y[i]));
		}
	}
	bfs(q2, q1, d+1);
}
/////////////////////
//SOLVE
void solve()
{
	cin >> n >> m;
	For(i,n)cin >> s[i];

	vis[0][0] = 1;

	queue<pii> q1, q2;
	q1.push(mp(0,0));
	bfs(q1,q2,1);

	cout << ans << endl;
	
	
}
/////////////////////
//MAIN
int main()
{
    FAST;
    ll t = 1;
//    cin >> t;
    while(t--)
    {
    solve();
    }
}
/////////////////////
/*
ZZZZZZZ     A        M     M     IIIIIII  N     N
     Z     A A      M M   M M       I     NN    N
    Z     A   A    M   M M   M      I     N N   N
   Z     AAAAAAA  M     M     M     I     N  N  N
  Z      A     A  M           M     I     N   N N
 Z       A     A  M           M     I     N    NN
ZZZZZZZ  A     A  M           M  IIIIIII  N     N  TREE
*/

Compilation message (stderr)

tracks.cpp: In function 'void bfs(std::queue<std::pair<long long int, long long int> >, std::queue<std::pair<long long int, long long int> >, long long int)':
tracks.cpp:19:27: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   19 | #define For(x, n) for(int (x) = 0 ; (x) < (n) ; (x)++)
      |                           ^
tracks.cpp:99:3: note: in expansion of macro 'For'
   99 |   For(i,4)
      |   ^~~
tracks.cpp: In function 'void solve()':
tracks.cpp:19:27: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   19 | #define For(x, n) for(int (x) = 0 ; (x) < (n) ; (x)++)
      |                           ^
tracks.cpp:123:2: note: in expansion of macro 'For'
  123 |  For(i,n)cin >> s[i];
      |  ^~~

• Subtask 1: 30 / 30
• Subtask 2: 61.25 / 70