Submission #444173

#	Time	Username	Problem	Language	Result	Execution time	Memory
444173		cpp219	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	1748 ms	141456 KiB

tracks

#pragma GCC optimization O2
#pragma GCC optimization "unroll-loop"
#pragma target ("avx2")

#include <bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 4e3 + 9;
const ll Log2 = 20;
const ll inf = 1e9 + 7;

char c;
ll n,m,a[N][N],cnt,ans,was[N][N];
ll dx[4] = {0,0,1,-1};
ll dy[4] = {1,-1,0,0};

bool chk(ll x,ll y){
    return x <= n&&y <= m&&x > 0&&y > 0;
}

queue<LL> q,differ;

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    cin>>n>>m;
    for (ll i = 1;i <= n;i++)
        for (ll j = 1;j <= m;j++){
            cin>>c; cnt += (c != '.');
            if (c == '.') a[i][j] = 2;
            if (c == 'F') a[i][j] = 1;
        }
    ll now = a[1][1],cur = 0; was[1][1] = 1; q.push({1,1});
    while(cur < cnt){
        ans++;
        while(!q.empty()){
            LL t = q.front(); q.pop(); cur++;
            for (ll i = 0;i < 4;i++){
                ll x = t.fs + dx[i],y = t.sc + dy[i];
                if (!chk(x,y) || was[x][y]) continue;
                was[x][y] = 1;
                if (a[x][y] == now) q.push({x,y});
                else if (a[x][y] == 1 - now) differ.push({x,y});
            }
        }
        //cout<<cur; return 0;
        now ^= 1;
        while(!differ.empty()) q.push(differ.front()),differ.pop();
    }
    cout<<ans;
}

Compilation message (stderr)

tracks.cpp:1: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    1 | #pragma GCC optimization O2
      | 
tracks.cpp:2: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    2 | #pragma GCC optimization "unroll-loop"
      | 
tracks.cpp:3: warning: ignoring '#pragma target ' [-Wunknown-pragmas]
    3 | #pragma target ("avx2")
      | 
tracks.cpp: In function 'int main()':
tracks.cpp:31:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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