Submission #1012641

#	Time	Username	Problem	Language	Result	Execution time	Memory
1012641		toast12	Mecho (IOI09_mecho)	C++14	100 / 100	157 ms	6464 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
 
const int MAXN = 800;
 
int n, s;
vector<vector<char>> grid;
vector<vector<int>> dist;
 
int honey;
 
bool reachable(int mecho, int bee) {
    return (((mecho-honey)/s < bee-honey) && mecho != -1); 
}
 
void bfs(queue<pair<int, int>> &q, vector<vector<int>> &d) {
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        if (x < 1 || y < 1 || x > n || y > n)
            continue;
        if (d[x+1][y] == -1 && grid[x+1][y] == '.' && reachable(d[x][y]+1, dist[x+1][y])) {
            q.push({x+1, y});
            d[x+1][y] = d[x][y]+1;
        }
        if (d[x-1][y] == -1 && grid[x-1][y] == '.' && reachable(d[x][y]+1, dist[x-1][y])) {
            q.push({x-1, y});
            d[x-1][y] = d[x][y]+1;
        }
        if (d[x][y+1] == -1 && grid[x][y+1] == '.' && reachable(d[x][y]+1, dist[x][y+1])) {
            q.push({x, y+1});
            d[x][y+1] = d[x][y]+1;
        }
        if (d[x][y-1] == -1 && grid[x][y-1] == '.' && reachable(d[x][y]+1, dist[x][y-1])) {
            q.push({x, y-1});
            d[x][y-1] = d[x][y]+1;
        }
    }
}
 
int main() {
    // ios_base::sync_with_stdio(0);
    // cin.tie(NULL);
    cin >> n >> s;
    grid.resize(n+2, vector<char>(n+2, '.'));
    pair<int, int> start, end;
    queue<pair<int, int>> q;
    dist.resize(n+2, vector<int>(n+2, -1));
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> grid[i][j];
            if (grid[i][j] == 'G')
                grid[i][j] = '.';
            else if (grid[i][j] == 'T')
                grid[i][j] = 'X';
            else if (grid[i][j] == 'M') {
                start = {i, j};
                grid[i][j] = '.';
            }
            else if (grid[i][j] == 'D') {
                end = {i, j};
                grid[i][j] = 'X';
            }
            else {
                q.push({i, j});
                dist[i][j] = 0;
            }
        }
    }
    // distance for bees
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        if (x < 1 || y < 1 || x > n || y > n)
            continue;
        if (dist[x+1][y] == -1 && grid[x+1][y] == '.') {
            q.push({x+1, y});
            dist[x+1][y] = dist[x][y]+1;
        }
        if (dist[x-1][y] == -1 && grid[x-1][y] == '.') {
            q.push({x-1, y});
            dist[x-1][y] = dist[x][y]+1;
        }
        if (dist[x][y+1] == -1 && grid[x][y+1] == '.') {
            q.push({x, y+1});
            dist[x][y+1] = dist[x][y]+1;
        }
        if (dist[x][y-1] == -1 && grid[x][y-1] == '.') {
            q.push({x, y-1});
            dist[x][y-1] = dist[x][y]+1;
        }
    }
    int lo = 0, hi = n*n;
    int ans = -1;
    while (lo <= hi) {
        int mid = (lo+hi)/2;
        // cout << mid << '\n';
        vector<vector<int>> d(n+2, vector<int>(n+2, -1));
        d[start.first][start.second] = mid;
        honey = mid;
        q.push(start);
        if (dist[start.first][start.second] <= mid)
            q.pop();
        bfs(q, d);
        bool poss = reachable(d[end.first-1][end.second], dist[end.first-1][end.second]);
        poss |= reachable(d[end.first+1][end.second], dist[end.first+1][end.second]);
        poss |= reachable(d[end.first][end.second-1], dist[end.first][end.second-1]);
        poss |= reachable(d[end.first][end.second+1], dist[end.first][end.second+1]);
        if (poss) {
            lo = mid+1;
            ans = mid;
        }
        else {
            hi = mid-1;
        }
    }
    cout << ans << '\n';
    return 0;
}

• Subtask 1: 100 / 100