Submission #1274243

#	Time	Username	Problem	Language	Result	Execution time	Memory
1274243		tkhoi13	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	600 ms	122144 KiB

tracks

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define db double
#define pii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define all(x) begin(x), end(x)
#define allr(x) rbegin(x), rend(x)
#define szx(x) ((int)(x).size())
#define FOR(i, a, b) for (int i = a, _b = (b); i <= _b; ++i)
#define ROF(i, a, b) for (int i = a, _b = (b); i >= _b; --i)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define endl '\n'
#define inf 1000000007
#define mod 1000000007

using namespace std;
using namespace __gnu_pbds;

void setIO(string filename = "") {
    ios::sync_with_stdio(0);
    cin.tie(0);
    if (!filename.empty()) {
        if (ifstream(filename + ".in")) {
            freopen((filename + ".in").c_str(), "r", stdin);
            freopen((filename + ".out").c_str(), "w", stdout);
        }
    }
}

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

int h, w;

vector<vector<char>> table;

bool valid(int x, int y) { return (x >= 0 && y >= 0 && x < h && y < w && table[x][y] != '.'); }

void solve() {
    cin >> h >> w;
    table.assign(h, vector<char>(w));
    REP(i, h) REP(j, w) cin >> table[i][j];

    int ans = 0;
    vector<vector<int>> dis(h, vector<int>(w, 1e9));

    deque<pii> dq;
    dq.pb({0, 0});
    dis[0][0] = 1;

    while (!dq.empty()) {
        pii v = dq.front();
        dq.pop_front();
        ans = max(ans, dis[v.fi][v.se]);

#define d(x) (x).fi][(x).se

        REP(i, 4) {
            if (valid(v.fi + dx[i], v.se + dy[i]) && dis[v.fi + dx[i]][v.se + dy[i]] == 1e9) {
                if (table[d(v)] == table[v.fi + dx[i]][v.se + dy[i]]) {
                    dis[v.fi + dx[i]][v.se + dy[i]] = dis[d(v)];
                    dq.push_front({v.fi + dx[i], v.se + dy[i]});
                } else {
                    dis[v.fi + dx[i]][v.se + dy[i]] = dis[d(v)] + 1;
                    dq.push_back({v.fi + dx[i], v.se + dy[i]});
                }
            }
        }
    }

    cout << ans;
}

void preprocess() {}

int main() {
    setIO("main");
    int t = 1;
    // cin >> t;
    preprocess();
    while (t--) { solve(); }
}

Compilation message (stderr)

tracks.cpp: In function 'void setIO(std::string)':
tracks.cpp:28:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |             freopen((filename + ".in").c_str(), "r", stdin);
      |             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:29:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |             freopen((filename + ".out").c_str(), "w", stdout);
      |             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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