Submission #960603

#	Time	Username	Problem	Language	Result	Execution time	Memory
960603		htphong0909	Mecho (IOI09_mecho)	C++17	100 / 100	137 ms	15368 KiB

mecho

#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
 
using ll = long long;
using ii = pair<int, int>;
 
const int N = 1e6+5;
const int INF = 1e9;
 
ll d[1000][1000],m[1000][1000],n,s;
char a[1000][1000];
ll dx[4]={1,0,0,-1};
ll dy[4]={0,1,-1,0};
ii pos,h;
 
bool bfs(ll x) {
    if (d[pos.fi][pos.se] - x * s <= 0) return 0;
    queue<ii> q;
    q.push(pos);
    for(int i=0;i<n;i++) {
        for(int j=0;j<n;j++) {
            m[i][j]=0;
        }
    }
    while(!q.empty()) {
        ii u=q.front();
        q.pop();
        for(int i=0;i<4;i++) {
            ii v={u.fi+dx[i],u.se+dy[i]};
            if(v.fi<0 || v.fi>=n || v.se<0 || v.se>=n) continue;
            if(m[v.fi][v.se]==0 && a[v.fi][v.se]!='T' &&
               d[v.fi][v.se]-x*s>m[u.fi][u.se]+1 && a[v.fi][v.se]!='M') {
                m[v.fi][v.se]=m[u.fi][u.se]+1;
                q.push(v);
            }
        }
    }
    if(m[h.fi][h.se]>0) return 1; else return 0;
}
 
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    queue<ii> q;
    cin >> n >> s;
    for(int i=0;i<n;i++) {
        for(int j=0;j<n;j++) {
            cin >> a[i][j];
            if(a[i][j]=='H') {
                q.push({i,j});
            }
            if(a[i][j]=='M') pos={i,j};
            if(a[i][j]=='D') h={i,j};
        }
    }
    while(!q.empty()) {
        ii u=q.front();
        q.pop();
        for(int i=0;i<4;i++) {
            ii v={u.fi+dx[i],u.se+dy[i]};
            if(v.fi<0 || v.fi>=n || v.se<0 || v.se>=n) continue;
            if(d[v.fi][v.se]==0 && a[v.fi][v.se]!='T' && a[v.fi][v.se]!='H' && a[v.fi][v.se]!='D') {
                d[v.fi][v.se]=d[u.fi][u.se]+s;
                q.push(v);
            }
        }
    }
    d[h.fi][h.se] = INF;
    ll l=0,r=99999999,ans=-1;
    while(l<=r) {
        ll m=(l+r)/2;
        if(bfs(m)) {
            ans=m;
            l=m+1;
        }
        else {
            r=m-1;
        }
    }
    cout << ans;
    return 0;
}

• Subtask 1: 100 / 100