Submission #869006

#	Time	Username	Problem	Language	Result	Execution time	Memory
869006		bobbilyking	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	604 ms	358288 KiB

tracks

#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")

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

typedef long long int ll;
typedef long double ld;
typedef pair<ll, ll> pl;

#define K first
#define V second
#define G(x) ll x; cin >> x;
#define GD(x) ld x; cin >> x;
#define GS(s) string s; cin >> s;
#define EX(x) { cout << x << '\n'; exit(0); }
#define A(a) (a).begin(), (a).end()
#define F(i, l, r) for (ll i = (l); i < r; ++i)

#define NN
#define M 1000000007 // 998244353

string grid[4010];
bool vis[4010][4010];
int main(){
//    freopen("a.in", "r", stdin);
//    freopen("a.out", "w", stdout);

    ios_base::sync_with_stdio(false); cin.tie(0);
    cout << fixed << setprecision(20);
    G(h) G(w)
    F(i, 0, h) cin >> grid[i];

    ll dx[4] = {0, -1, 0, 1};
    ll dy[4] = {1, 0, -1, 0};

    vector<pl> q{pl{0, 0}, pl{h-1, w-1}};
    vector<pl> nq;
    char cur = grid[0][0]; // character we are currently looking at
    ll iter = 0;
    vis[0][0] = vis[h-1][w-1] = 1;
    
    for (; q.size(); iter++, cur = cur == 'R' ? 'F' : 'R') {
        F(ha, 0, q.size()) {
            auto [x, y] = q[ha];
            F(k, 0, 4) {
                ll ni = x + dx[k], nj = y + dy[k];
                if (min(ni, nj) >= 0 and ni < h and nj < w and grid[ni][nj] != '.' and !vis[ni][nj]) {
                    vis[ni][nj] = 1;
                    if (grid[ni][nj] == cur) q.emplace_back(ni, nj);
                    else nq.emplace_back(ni, nj);
                }
            }
        }
        q.clear(); swap(q, nq);
    }

    cout << iter << '\n';
}

Compilation message (stderr)

tracks.cpp: In function 'int main()':
tracks.cpp:20:39: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 | #define F(i, l, r) for (ll i = (l); i < r; ++i)
......
   46 |         F(ha, 0, q.size()) {
      |           ~~~~~~~~~~~~~~~              
tracks.cpp:46:9: note: in expansion of macro 'F'
   46 |         F(ha, 0, q.size()) {
      |         ^

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