Submission #59164

#	Time	Username	Problem	Language	Result	Execution time	Memory
59164		Benq	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	1309 ms	109468 KiB

tracks

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()

const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 4000*4000;

int H,W, dist[4000][4000];
bool done[4000][4000];
string g[4000];
int xd[4] = {0,1,0,-1}, yd[4] = {1,0,-1,0};

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> H >> W;
    F0R(i,H) cin >> g[i];
    
    F0R(i,H) F0R(j,W) dist[i][j] = MOD;
    
    deque<int> q; dist[0][0] = 0; q.pb(0);
    int ans = 0;
    while (sz(q)) {
        int x = q.front(); q.pop_front();
        int y = x%W; x /= W;
        if (done[x][y]) continue;
        done[x][y] = 1;
        ans = max(ans,dist[x][y]);
        F0R(i,4) {
            int X = x+xd[i], Y = y+yd[i];
            if (X < 0 || X >= H || Y < 0 || Y >= W) continue;
            if (g[X][Y] == '.') continue;
            if (g[X][Y] == g[x][y]) {
                if (dist[X][Y] > dist[x][y]) {
                    dist[X][Y] = dist[x][y];
                    q.push_front(W*X+Y);
                }
            } else {
                if (dist[X][Y] > dist[x][y]+1) {
                    dist[X][Y] = dist[x][y]+1;
                    q.pb(W*X+Y);
                }
            }
        }
    }
    cout << ans+1;
}

/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

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