Submission #1212252

#	Time	Username	Problem	Language	Result	Execution time	Memory
1212252		pleth	Mecho (IOI09_mecho)	C++20	100 / 100	152 ms	6472 KiB

mecho

#include <climits>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;

int n, s;
vector<string> forest;
vector<vector<int>> beeDist;
int xStart, yStart, xEnd, yEnd;
vector<int> dirx = {1, 0, -1, 0}, diry = {0, 1, 0, -1};
vector<vector<int>> mechoTime;

bool mecho(int wait) {
    if(wait>=beeDist[xStart][yStart]) {
        return false;
    }
    queue<pair<int, int>> q;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            mechoTime[i][j] = INT_MAX;
        }
    }
    mechoTime[xStart][yStart] = 0;
    q.push({xStart, yStart});
    while (!q.empty()) {
        int x = q.front().first, y = q.front().second;
        q.pop();
        for (int i = 0; i < 4; i++) {
            int nextX = x + dirx[i], nextY = y + diry[i];
            if (nextX >= 0 && nextX < n && nextY >= 0 && nextY < n &&
                mechoTime[nextX][nextY] > mechoTime[x][y] + 1 &&
                forest[nextX][nextY] != 'T' && forest[nextX][nextY]!='D' &&
                beeDist[nextX][nextY] * s > (mechoTime[x][y] + 1) + wait * s) {
                mechoTime[nextX][nextY] = mechoTime[x][y] + 1;
                q.push({nextX, nextY});
            }
        }
    }
    for (int i = 0; i < 4; i++) {
        int nextX = xEnd + dirx[i], nextY = yEnd + diry[i];
        if (nextX >= 0 && nextX < n && nextY >= 0 && nextY < n &&
            mechoTime[nextX][nextY] != INT_MAX) {
            return true;
        }
    }
    return false;
}

int main() {
    cin >> n >> s;
    forest.resize(n);
    for (int i = 0; i < n; i++) {
        cin >> forest[i];
    }
    queue<pair<int, int>> q;
    beeDist.resize(n, vector<int>(n, INT_MAX));
    mechoTime.resize(n, vector<int>(n));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (forest[i][j] == 'H') {
                q.push({i, j});
                beeDist[i][j] = 0;
            } else if (forest[i][j] == 'M') {
                xStart = i;
                yStart = j;
            } else if (forest[i][j] == 'D') {
                xEnd = i;
                yEnd = j;
            }
        }
    }
    while (!q.empty()) {
        int x = q.front().first, y = q.front().second;
        q.pop();
        for (int i = 0; i < 4; i++) {
            int nextX = x + dirx[i], nextY = y + diry[i];
            if (nextX >= 0 && nextX < n && nextY >= 0 && nextY < n &&
                forest[nextX][nextY] != 'T' && forest[nextX][nextY] != 'D' &&
                beeDist[nextX][nextY] > beeDist[x][y] + 1) {
                beeDist[nextX][nextY] = beeDist[x][y] + 1;
                q.push({nextX, nextY});
            }
        }
    }
    int l = 0, r = n * n;
    while (l <= r) {
        int m = (r - l) / 2 + l;
        if (mecho(m)) {
            l = m + 1;
        } else {
            r = m - 1;
        }
    }
    cout << r << endl;
}

• Subtask 1: 100 / 100