Submission #710517

#	Time	Username	Problem	Language	Result	Execution time	Memory
710517		hafo	Tracks in the Snow (BOI13_tracks)	C++14	0 / 100	839 ms	138968 KiB

tracks

#include <bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define pb push_back
#define pa pair<int, int>
#define pall pair<ll, int>
#define fi first
#define se second
#define TASK "test"
#define all(x) x.begin(), x.end()
using namespace std;

template<typename T1, typename T2> bool mini (T1 &a, T2 b) {if(a > b) a = b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi (T1 &a, T2 b) {if(a < b) a = b; else return 0; return 1;}

const int MOD = 1e9 + 7;
const int LOG = 20;
const int maxn = 4e3 + 7;
const ll oo = 1e17 + 69;

int n, m, f[maxn][maxn];
char a[maxn][maxn];
pa d[] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

void bfs() {
    deque<pa> q;
    memset(f, -1, sizeof f);
    f[0][0] = 0;
    q.push_front({0, 0});
    int ans = 0;

    while(!q.empty()) {
        int u = q.front().fi;
        int v = q.front().se;
        q.pop_front();
        maxi(ans, f[u][v]);

        for(int k = 0; k < 4; k++) {
            int x = u + d[k].fi;
            int y = v + d[k].se;
            if(x < 0 || x == n || y < 0 || y == m || f[x][y] != -1) continue;
            int w = (a[u][v] != a[x][y]);
            f[x][y] = f[u][v] + w;
            if(w) q.pb({x, y});
            else q.push_front({x, y});
        }
    }
    cout<<ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    //freopen(TASK".inp", "r", stdin);
    //freopen(TASK".out", "w", stdout);

    cin>>n>>m;
    for(int i = 0; i < n; i++)
        for(int j = 0; j < m; j++) cin>>a[i][j];
    bfs();
    return 0;
}

• Subtask 1: 0 / 30
• Subtask 2: 0 / 70