Submission #499321

#	Time	Username	Problem	Language	Result	Execution time	Memory
499321		tphuc2908	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	1673 ms	167168 KiB

tracks

#include<bits/stdc++.h>

using namespace std;
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
//#pragma GCC optimization ("unroll-loops")
#define rep(i, x, y) for(int i = x; i <= y; ++i)
#define repi(i,x,y) for(int i = x; i >= y; --i)
#define ci(x) int x; cin>> x
#define TC(t) ci(t); while(t--)
#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define cii(x, y) ci(x); ci(y)
#define ciii(x, y, z) ci(x); ci(y); ci(z)
#define mp make_pair
//#define int long long
typedef long long ll;
typedef vector<int> vi;
const int N = 4e3 + 5;
const int mod = 1e9 + 7;
const int mod1 = 1e9 + 9;
const int pi = 31;
const int inf = 1e9 + 5;
const int block = 330;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

void readfile(){
    #ifdef ONLINE_JUDGE
    #else
        freopen("text.inp", "r", stdin);
    #endif // ONLINE_JUDGE
//    freopen("248.in", "r", stdin);
//    freopen("248.out", "w", stdout);
}

int n, m;
char a[N][N];

void inp(){
    cin >> n >> m;
    rep(i,1,n)
        rep(j,1,m)
            cin >> a[i][j];
}

queue<pair<int,int> > q[2];
int d[N][N], vis[N][N];

void bfs(int x, int y){
    rep(i,1,n)
        rep(j,1,m)
            d[i][j] = inf;
    d[x][y] = 1;
    q[1].push(mp(x, y));
    int num = 1, pos = 1;
    while(num){
        while(q[pos % 2].empty())
            ++pos;
        auto top = q[pos % 2].front();
        q[pos % 2].pop(), --num;
        if(vis[top.fi][top.se]) continue;
        vis[top.fi][top.se] = 1;
        rep(i,0,3){
            int x = top.fi + dx[i];
            int y = top.se + dy[i];
            if(1 <= x && x <= n && 1 <= y && y <= m && a[x][y]!='.'){
                int cost = (a[x][y] != a[top.fi][top.se]);
                if(d[x][y] > d[top.fi][top.se] + cost){
                    d[x][y] = d[top.fi][top.se] + cost;
                    q[d[x][y] % 2].push(mp(x, y));
                    ++num;
                }
            }
        }
    }
}

void process(){
    bfs(1,1);
    int res = 0;
    rep(i,1,n)
        rep(j,1,m)
            if(d[i][j]!=inf)
                res = max(res, d[i][j]);
    cout << res;
}

int main() {
   // readfile();
    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    TC(t){
        inp();
        process();
//    }
    return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'void readfile()':
tracks.cpp:33:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |         freopen("text.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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