Submission #642192

#	Time	Username	Problem	Language	Result	Execution time	Memory
642192		Ronin13	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	1995 ms	345400 KiB

tracks

#include <bits/stdc++.h>
#define ll long long
#define f first
#define s second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define epb emplace_back
#define ull unsigned ll
using namespace std;

int d[4005][4005];
char c[4005][4005];
bool used[4005][4005];

int main(){
    int n, m; cin >> n >> m;
    for(int i = 0; i <= n + 1; i++){
        for(int j= 0; j <= m + 1; j++) c[i][j] = '.';
    }
    for(int i= 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            cin >> c[i][j];
            d[i][j] = 1e9;
        }
    }

    deque <pii> q;
    q.push_front({1, 1});
    d[1][1] = 1;
    int ans = 0;
    while(!q.empty()){
        pii v = q.front(); q.pop_front();

        if(used[v.f][v.s] == true) continue;
        ans = max(ans, d[v.f][v.s]);
        used[v.f][v.s] = true;
        int x = v.f, y = v.s;
        if(c[x - 1][y] != '.'){
            int len = (c[x - 1][y] != c[x][y]);
            d[x - 1][y] = min(d[x - 1][y], d[x][y] + len);
            if(len) q.pb({x - 1, y});
            else q.push_front({x - 1, y});
        }
        if(c[x + 1][y] != '.'){
            int len = (c[x + 1][y] != c[x][y]);
            d[x + 1][y] = min(d[x + 1][y], d[x][y] + len);
            if(len) q.pb({x + 1, y});
            else q.push_front({x + 1, y});
        }
        if(c[x][y - 1] != '.'){
            int len = (c[x][y - 1] != c[x][y]);
            d[x][y - 1] = min(d[x][y - 1], d[x][y] + len);
            if(len) q.pb({x, y -1});
            else q.push_front({x, y - 1});
        }
         if(c[x][y + 1] != '.'){
            int len = (c[x][y + 1] != c[x][y]);
            d[x][y + 1] = min(d[x][y + 1], d[x][y] + len);
            if(len) q.pb({x, y +1});
            else q.push_front({x, y + 1});
        }
    }
    cout << ans;
    return 0;
}

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