Submission #335497

#	Time	Username	Problem	Language	Result	Execution time	Memory
335497		DavidDamian	Mecho (IOI09_mecho)	C++11	41 / 100	213 ms	9552 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> pii;
char forest[805][805];
int n,s;
queue<pii> Q;
int timeBees[805][805];
int dx[4]={1,-1,0,0};
int dy[4]{0,0,1,-1};
void bfsBees(vector<pii> source){
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            timeBees[i][j]=INT_MAX;
        }
    }
    for(pii u: source){
        timeBees[u.first][u.second]=0;
        Q.push(u);
    }
    while(!Q.empty()){
        pii u=Q.front();
        Q.pop();
        for(int mov=0;mov<4;mov++){
            int i=u.first+dx[mov];
            int j=u.second+dy[mov];
            if(i<1 || i>n) continue;
            if(j<1 || j>n) continue;
            if(forest[i][j]=='T' || forest[i][j]=='D') continue;
            if(timeBees[i][j]==INT_MAX){
                timeBees[i][j]=timeBees[u.first][u.second]+1;
                Q.push(pii(i,j));
            }
        }
    }
}
pii start;
pii goal;
int dist[805][805];
int fuel[805][805];
bool valid(int moment){
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            dist[i][j]=INT_MAX;
        }
    }
    dist[start.first][start.second]=moment;
    fuel[start.first][start.second]=0;
    Q.push(start);
    while(!Q.empty()){
        pii u=Q.front();
        Q.pop();
        for(int mov=0;mov<4;mov++){
            int i=u.first+dx[mov];
            int j=u.second+dy[mov];
            if(i<1 || i>n) continue;
            if(j<1 || j>n) continue;
            if(forest[i][j]=='T' || forest[i][j]=='H') continue;
            int nxt_dist=dist[u.first][u.second];
            if(fuel[u.first][u.second]==0)
                nxt_dist++;
            if(timeBees[i][j]<nxt_dist) continue;
            if(fuel[u.first][u.second]==1 && timeBees[i][j]==nxt_dist) continue;
            if(dist[i][j]==INT_MAX){
                dist[i][j]=nxt_dist;
                fuel[i][j]=(fuel[u.first][u.second]>0)? fuel[u.first][u.second]-1 : s-1;
                Q.push(pii(i,j));
            }
        }
    }
    return dist[goal.first][goal.second]!=INT_MAX;
}
int binarySearch(){
    int L=0,R=1600;
    int mid=(L+R)/2;
    int ans=-1;
    while(L<=R){
        mid=(L+R)/2;
        if(valid(mid)){
            ans=mid;
            L=mid+1;
        }
        else{
            R=mid-1;
        }
    }
    return ans;
}
int main()
{
    vector<pii> beeSource;
    cin>>n>>s;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>forest[i][j];
            if(forest[i][j]=='H'){
                beeSource.push_back(pii(i,j));
            }
            else if(forest[i][j]=='M'){
                start=pii(i,j);
            }
            else if(forest[i][j]=='D'){
                goal=pii(i,j);
            }
        }
    }
    bfsBees(beeSource);
    int last=binarySearch();
    cout<<last<<'\n';
    return 0;
}

• Subtask 1: 41 / 100