Submission #998318

#	Time	Username	Problem	Language	Result	Execution time	Memory
998318		AtinaR	Mecho (IOI09_mecho)	C++14	38 / 100	136 ms	11888 KiB

mecho

#include <bits/stdc++.h>

using namespace std;
const long long MAX=810;
long long n,s;
char mat[MAX][MAX];
long long si,sj,ei,ej;
long long di[4]= {0,0,-1,1};
long long dj[4]= {1,-1,0,0};
vector<pair<long long,long long> > hives;
long long distmecho[MAX][MAX];
long long occupied[MAX][MAX];
bool canspreadhive(long long i, long long j)
{
    if(i<0 || i>=n || j<0 || j>=n || occupied[i][j]!=-1 || mat[i][j]=='T' || mat[i][j]=='D')return false;
    return true;
}
void spread_hives()
{
    memset(occupied,-1,sizeof(occupied));
    queue<pair<long long,long long> > q;
    for(auto x:hives)
    {
        q.push(x);
        occupied[x.first][x.second]=0;
    }
    while(!q.empty())
    {
        auto curr=q.front();
        q.pop();
        for(long long k=0; k<4; k++)
        {
            long long newi=curr.first+di[k];
            long long newj=curr.second+dj[k];
            if(!canspreadhive(newi,newj))continue;
            occupied[newi][newj]=occupied[curr.first][curr.second]+1;
            q.push({newi,newj});
        }
    }
}
bool canmechostep(long long i, long long j)
{
    if(i<0 || i>=n || j<0 || j>=n || distmecho[i][j]!=-1 || mat[i][j]=='H' || mat[i][j]=='T')return false;
    return true;
}
bool can_stay(long long X)
{
    memset(distmecho,-1,sizeof(distmecho));
    distmecho[si][sj]=0;
    queue<pair<long long,long long> > q;
    q.push({si,sj});
    while(!q.empty())
    {
        auto curr=q.front();
        q.pop();
        for(long long k=0; k<4; k++)
        {
            long long newi=curr.first+di[k];
            long long newj=curr.second+dj[k];
            if(!canmechostep(newi,newj))continue;
            long long newtime=distmecho[curr.first][curr.second]+1;
            long long tmp=newtime;
            long long use=tmp/s+X;
            if(tmp%s)use++;
            if(use<=occupied[newi][newj] || newi==ei && newj==ej)
            {
                distmecho[newi][newj]=newtime;
                q.push({newi,newj});
            }
        }
    }
    if(distmecho[ei][ej]!=-1)return true;
    else return false;
}
int main()
{
    cin>>n>>s;
    for(long long i=0; i<n; i++)
    {
        for(long long j=0; j<n; j++)
        {
            cin>>mat[i][j];
            if(mat[i][j]=='M')
            {
                si=i;
                sj=j;
            }
            else if(mat[i][j]=='D')
            {
                ei=i;
                ej=j;
            }
            else if(mat[i][j]=='H')
            {
                hives.push_back({i,j});
            }
        }
    }
    spread_hives();
    long long B=0,E=1e6;
    long long res=-1;
    while(B<=E)
    {
        long long mid=(B+E)/2;
        if(can_stay(mid))
        {
            res=mid;
            B=mid+1;
        }
        else
        {
            E=mid-1;
        }
    }
    cout<<res<<endl;
    return 0;
}

Compilation message (stderr)

mecho.cpp: In function 'bool can_stay(long long int)':
mecho.cpp:65:54: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   65 |             if(use<=occupied[newi][newj] || newi==ei && newj==ej)
      |                                             ~~~~~~~~~^~~~~~~~~~~

• Subtask 1: 38 / 100