Submission #957744

#	Time	Username	Problem	Language	Result	Execution time	Memory
957744		hirayuu_oj	Mecho (IOI09_mecho)	C++17	84 / 100	182 ms	11860 KiB

mecho

#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); i++)
#define rep2(i,a,b) for(int i=a; i<(b); i++)
#define all(x) x.begin(),x.end()
using ll=long long;
const ll INF=1LL<<60;
const int four[5]={0,1,0,-1,0};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    ll s;
    cin>>n>>s;
    vector<string> forest(n);
    rep(i,n){
        cin>>forest[i];
    }
    vector<vector<ll>> bee(n,vector<ll>(n,INF));
    queue<pair<int,int>> vert;
    rep(i,n){
        rep(j,n){
            if(forest[i][j]=='H'){
                bee[i][j]=0;
                vert.push({i,j});
            }
        }
    }
    while(!vert.empty()){
        int x,y;
        tie(x,y)=vert.front();
        vert.pop();
        rep(i,4){
            int nx=x+four[i],ny=y+four[i+1];
            if(nx<0 or n<=nx or ny<0 or n<=ny){
                continue;
            }
            if(forest[nx][ny]!='G'){
                continue;
            }
            if(bee[nx][ny]>bee[x][y]+1){
                bee[nx][ny]=bee[x][y]+1;
                vert.push({nx,ny});
            }
        }
    }
    int hx,hy;
    rep(i,n){
        rep(j,n){
            if(forest[i][j]=='D'){
                hx=i;
                hy=j;
            }
        }
    }
    ll ok=-1,ng=n*n+1000;
    vector<vector<ll>> dist(n,vector<ll>(n));
    while(ng-ok>1){
        ll mid=(ok+ng)>>1;
        rep(i,n){
            rep(j,n){
                if(forest[i][j]=='M'){
                    dist[i][j]=mid*s;
                    vert.push({i,j});
                }
                else{
                    dist[i][j]=INF;
                }
            }
        }
        bool can=false;
        while(!vert.empty()){
            int x,y;
            tie(x,y)=vert.front();
            vert.pop();
            rep(i,4){
                int nx=x+four[i],ny=y+four[i+1];
                if(nx<0 or n<=nx or ny<0 or n<=ny){
                    continue;
                }
                if(forest[nx][ny]=='D'){
                    can=true;
                }
                if(forest[nx][ny]!='G'){
                    continue;
                }
                if((dist[x][y]+1)/s>=bee[nx][ny]){
                    continue;
                }
                if(dist[nx][ny]>dist[x][y]+1){
                    dist[nx][ny]=dist[x][y]+1;
                    vert.push({nx,ny});
                }
            }
        }
        if(can){
            ok=mid;
        }
        else{
            ng=mid;
        }
    }
    cout<<ok<<"\n";
}

Compilation message (stderr)

mecho.cpp: In function 'int main()':
mecho.cpp:48:9: warning: variable 'hx' set but not used [-Wunused-but-set-variable]
   48 |     int hx,hy;
      |         ^~
mecho.cpp:48:12: warning: variable 'hy' set but not used [-Wunused-but-set-variable]
   48 |     int hx,hy;
      |            ^~

• Subtask 1: 84 / 100