Submission #490322

#	Time	Username	Problem	Language	Result	Execution time	Memory
490322		XII	Tracks in the Snow (BOI13_tracks)	C++17	44.17 / 100	2097 ms	78532 KiB

tracks

#include <bits/stdc++.h>
using namespace std;

using ll = long long;

#define fi first
#define se second
#define mp make_pair
#define eb emplace_back
#define ALL(x) (x).begin(), (x).end()

#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORU(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)

#define IOS cin.tie(0)->sync_with_stdio(false);
#define PROB "BOI13_tracks"
void Fi(){
    if(fopen(PROB".inp", "r")){
        freopen(PROB".inp", "r", stdin);
        freopen(PROB".out", "w", stdout);
    }
}

const int N = 4e3 + 1;
int a[N][N], n, m;
int F, R;

int encode(const char &c){
    switch(c){
        case '.': return 0;
        case 'F': ++F; return 1;
        case 'R': ++R; return -1;
    }
}

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

using pi = pair<int, int>;
queue<pi> qe;

void bfs(int ani){
    int tmp = 1;
    qe.emplace(1, 1); a[1][1] = -ani;
    while(!qe.empty()){
        auto [x, y] = qe.front(); qe.pop();
        FOR(d, 0, 4){
            int i = x + dx[d];
            int j = y + dy[d];
            if(i < 1 || n < i || j < 1 || m < i) continue;
            if(a[i][j] == ani){
                a[i][j] = -ani;
                ++tmp;
                qe.emplace(i, j);
            }
        }
    }
    if(ani == 1) F -= tmp, R += tmp;
    else F += tmp, R -= tmp;
}

int main(){
    IOS;
    Fi();
    cin >> n >> m;
    FORU(i, 1, n){
        string s; cin >> s;
        FORU(j, 1, m){
            a[i][j] = encode(s[j - 1]);
        }
    }
    int ans = 1;
    while(R && F){
        bfs(a[1][1]);
        ++ans;
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'void Fi()':
tracks.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |         freopen(PROB".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |         freopen(PROB".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp: In function 'int encode(const char&)':
tracks.cpp:35:1: warning: control reaches end of non-void function [-Wreturn-type]
   35 | }
      | ^

• Subtask 1: 26.666666666666668 / 30
• Subtask 2: 17.5 / 70