Submission #595044

#	Time	Username	Problem	Language	Result	Execution time	Memory
595044		ShivanshJ	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	1766 ms	922000 KiB

tracks

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int MAX=4e3+5;
const int INF=1e18;
const int MOD=1e9+7;
const int MAXL=32;
int dx[]={-1,0,1,0},dy[]={0,1,0,-1};
int g[MAX][MAX][6],h,w; // {T,R,B,L} , vertex-info (4)
bool chk(int x,int y) {
    return (x>=0 && y>=0 && x<h && y<w && g[x][y][4]!=-1);
}
signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    //cout<<setprecision(6)<<fixed;
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);

    cin>>h>>w;
    for(int i=0;i<h;i++) {
        for(int j=0;j<w;j++) {
            char s;
            cin>>s;
            if(s=='R') {
                g[i][j][4]=0;
            } else if(s=='F') {
                g[i][j][4]=1;
            } else {
                g[i][j][4]=-1;
            }
        }
    }
    for(int i=0;i<h;i++) {
        for(int j=0;j<w;j++) {
            for(int z=0;z<4;z++) {
                int nx=i+dx[z],ny=j+dy[z];
                if(chk(nx,ny) && g[nx][ny][4]!=g[i][j][4]) {
                    g[i][j][z]=1;
                }
            }
            g[i][j][5]=-1;
        }
    }
    deque<tuple<int,int,int>>dq; //{x,y,dist}
    dq.push_front({0,0,0});
    int ans=0;
    while(!dq.empty()) {
        tuple<int,int,int>curr=dq.front();
        dq.pop_front();
        int x=get<0>(curr),y=get<1>(curr),d=get<2>(curr);
        if(g[x][y][5]!=-1) {
            continue;
        }
        g[x][y][5]=d;
        ans=max(ans,d);
        for(int i=0;i<4;i++) {
            int nx=x+dx[i],ny=y+dy[i];
            if(!chk(nx,ny) || g[nx][ny][5]!=-1) {
                continue;
            }
            if(g[x][y][i]) {
                dq.push_back({nx,ny,d+1});
            } else {
                dq.push_front({nx,ny,d});
            }
        }
    }
    cout<<(++ans);
    return 0;
}

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