Submission #842508

#	Time	Username	Problem	Language	Result	Execution time	Memory
842508		saturina	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	548 ms	241232 KiB

tracks

//made by Nguyễn Hồng Nam
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
const ll mod = 1e9 + 7,inf = 1e18,mxn = 4005;
#define pll pair<ll,ll>
#define fi first
#define se second
deque<pll> q;
ll d[mxn][mxn],h,w,row[4] = {-1,0,0,1},col[4] = {0,-1,1,0},ans = 1;
string s[mxn];
void maxz(ll &a,ll b)
{
    if(a < b) a= b;
}
bool check(ll i,ll j)
{
    if(i >= 0 && i < h && j >= 0 && j < w && s[i][j] != '.') return true;
    return false;
}
void bfs01()
{
    d[0][0] = 1;
    q.push_back({0,0});
    while(!q.empty())
    {
        pll mx = q.front();
        maxz(ans,d[mx.fi][mx.se]);
        q.pop_front();
        for(ll i = 0; i < 4; i++)
        {
            ll a = mx.fi + row[i],b = mx.se + col[i];
            if(check(a,b) && d[a][b] == 0)
            {
                if(s[a][b] == s[mx.fi][mx.se])
                {
                    d[a][b] = d[mx.fi][mx.se];
                    q.push_front({a,b});
                }
                else
                {
                    d[a][b] = d[mx.fi][mx.se] + 1;
                    q.push_back({a,b});
                }
            }
        }
    }
}
int main()
{
#define taskname "track"
    if (fopen(taskname".inp", "r"))
    {
        freopen(taskname".inp", "r", stdin);
        freopen(taskname".out", "w", stdout);
    }
    cin.tie(0)->sync_with_stdio(0);
    cin >> h >> w;
    for(ll i = 0; i < h; i++)
    {
        cin >> s[i];
    }
    bfs01();
    cout << ans << '\n';
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'int main()':
tracks.cpp:56:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:57:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |         freopen(taskname".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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