Submission #1084370

#	Time	Username	Problem	Language	Result	Execution time	Memory
1084370		PhamKhanhHuyen	Mecho (IOI09_mecho)	C++14	79 / 100	148 ms	7160 KiB

mecho

#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
using namespace std;

int n, s;
const int maxn = 1000;
const int inf = 1e9;
char a[maxn + 3][maxn + 3];
pii st, en;
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};

bool valid(int i, int j)
{
    return (i >= 1 && j >= 1 && i <= n && j <= n);
}

bool reach(int x, int y)
{
    return x/s < y;
}

int main()
{
   // freopen("metro.in", "r", stdin);
   // freopen("metro.out", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> s;
    vector<vector<int>>time(n + 3, vector<int>(n + 3, inf));

    queue<pii>q;

    for(int i = 1; i <= n; ++i)
    {
        for(int j = 1; j <= n; ++j)
        {
            cin >> a[i][j];
            if(a[i][j] == 'M') st.fi = i, st.se = j;
            else if(a[i][j] == 'D')
            {
                en.fi = i, en.se = j;
            }
            else if(a[i][j] == 'H')
            {
                q.push({i, j});
                time[i][j] = 0;
            }

        }
    }

    while(!q.empty())
    {
        int x = q.front().fi;
        int y = q.front().se;
        q.pop();
        for(int k = 0; k < 4; k++)
        {
            int i = x + dx[k];
            int j = y + dy[k];
            if(valid(i, j) && (a[i][j] == 'G' || a[i][j] == 'M') && time[i][j] == inf)
            {
                q.push({i, j});
                time[i][j] = time[x][y] + 1;
            }
        }
    }
    /*for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= n; j++)
        {
            cout << time[i][j] << ' ';
        } cout << '\n';
    }*/
    int l = 0, r = n * n, mid, res = 0;
    while(l <= r)
    {
        mid = (l + r) / 2;
        vector<vector<int>>mecho_time(n + 3, vector<int>(n + 3, inf));
        mecho_time[st.fi][st.se] = 0;
        q.push(st);
        if(time[st.fi][st.se] <= mid){
            q.pop();
        }
        while(!q.empty()){
            int x = q.front().fi;
            int y = q.front().se;
            q.pop();
            for(int k = 0; k < 4; k++)
            {
                int i = x + dx[k];
                int j = y + dy[k];
                if(valid(i, j) && (a[i][j] == 'G' || a[i][j] == 'M') && mecho_time[i][j] == inf && reach(mecho_time[x][y] + 1, time[i][j] - mid))
                {
                    q.push({i, j});
                    mecho_time[i][j] = mecho_time[x][y] + 1;
                }
            }
        }
        bool Reach = false;
        for(int i = 0; i < 4; i++)
        {
            int nx = en.fi + dx[i], ny = en.se + dy[i];
            if(valid(nx, ny) && (a[nx][ny] == 'G' || a[nx][ny] == 'M') && reach(mecho_time[nx][ny], time[nx][ny] - mid))
            {
                Reach = true;
                break;
            }
        }
        if(Reach) {
            res = mid;
            l = mid + 1;
        }
        else r = mid - 1;
    }
    if(res)cout << res;
    else cout << -1;
}

• Subtask 1: 79 / 100