Submission #386569

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
386569	2021-04-06T21:58:54 Z	SansPapyrus683	Mecho (IOI09_mecho)	C++17	100 / 100	632 ms	7008 KB

mecho

#include <iostream>
#include <vector>
#include <queue>
#include <climits>

using std::cout;
using std::endl;
using std::vector;
using std::pair;

vector<pair<int, int>> neighbors(const pair<int, int>& at, int row_num, int col_num) {
    vector<pair<int, int>> neighbors;
    if (at.first > 0) {
        neighbors.push_back({at.first - 1, at.second});
    }
    if (at.second > 0) {
        neighbors.push_back({at.first, at.second - 1});
    }
    if (at.first < row_num - 1) {
        neighbors.push_back({at.first + 1, at.second});
    }
    if (at.second < col_num - 1) {
        neighbors.push_back({at.first, at.second + 1});
    }
    return neighbors;
}

class Field {
    private:
        const vector<vector<char>> field;
        const int row_num;
        const int col_num;
        pair<int, int> start;
        vector<vector<int>> bee_dists;
    public:
        Field(const vector<vector<char>>& field)
                : field(field), row_num(field.size()), col_num(field[0].size()),
                  bee_dists(row_num, vector<int>(col_num, INT_MAX)) {
            std::queue<pair<int, int>> frontier;
            for (int r = 0; r < row_num; r++) {
                for (int c = 0; c < col_num; c++) {
                    if (field[r][c] == 'H') {
                        frontier.push({r, c});
                        bee_dists[r][c] = 0;
                    } else if (field[r][c] == 'M') {
                        start = {r, c};
                    }
                }
            }
            
            while (!frontier.empty()) {
                pair<int, int> c = frontier.front();  // c for curr and to reduce my line length
                frontier.pop();
                int n_cost = bee_dists[c.first][c.second] + 1;
                for (const pair<int, int>& n : neighbors(c, row_num, col_num)) {
                    if (n_cost < bee_dists[n.first][n.second]
                            && field[n.first][n.second] != 'T'
                            && field[n.first][n.second] != 'D') {
                        bee_dists[n.first][n.second] = n_cost;
                        frontier.push(n);
                    }
                }
            }
        }

        bool can_go_home(int honey_time, int speed) {
            if (bee_dists[start.first][start.second] <= honey_time) {
                return false;
            }
            std::queue<pair<int, int>> frontier;
            vector<vector<int>> min_moves(row_num, vector<int>(col_num, INT_MAX));
            frontier.push(start);  // dw, we checked if the start was valid literally above
            min_moves[start.first][start.second] = honey_time * speed;
            while (!frontier.empty()) {
                pair<int, int> curr = frontier.front();
                frontier.pop();
                if (field[curr.first][curr.second] == 'D') {
                    return true;
                }
                int n_cost = min_moves[curr.first][curr.second] + 1;
                for (const pair<int, int>& n : neighbors(curr, row_num, col_num)) {
                    if (field[n.first][n.second] != 'T'
                            && (n_cost / speed) < bee_dists[n.first][n.second]
                            && n_cost < min_moves[n.first][n.second]) {
                        min_moves[n.first][n.second] = n_cost;
                        frontier.push(n);
                    }
                }
            }
            return false;
        }
};

// https://oj.uz/problem/view/IOI09_mecho (sample input ommitted)
int main() {
    int side_len;
    int speed;
    std::cin >> side_len >> speed;
    vector<vector<char>> grid(side_len, vector<char>(side_len));
    for (int r = 0; r < side_len; r++) {
        for (int c = 0; c < side_len; c++) {
            std::cin >> grid[r][c];
        }
    }

    Field field(grid);
    int lo = 0;
    int hi = side_len * side_len;
    int valid = -1;
    while (lo <= hi) {
        int mid = (lo + hi) / 2;
        if (field.can_go_home(mid, speed)) {
            valid = mid;
            lo = mid + 1;
        } else {
            hi = mid - 1;
        }
    }
    cout << valid << endl;
}

Subtask #1

100.0 / 100.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	1 ms	364 KB	Output is correct
2	Correct	1 ms	364 KB	Output is correct
3	Correct	1 ms	364 KB	Output is correct
4	Correct	1 ms	384 KB	Output is correct
5	Correct	1 ms	256 KB	Output is correct
6	Correct	1 ms	364 KB	Output is correct
7	Correct	469 ms	6904 KB	Output is correct
8	Correct	1 ms	364 KB	Output is correct
9	Correct	2 ms	364 KB	Output is correct
10	Correct	1 ms	364 KB	Output is correct
11	Correct	1 ms	364 KB	Output is correct
12	Correct	1 ms	364 KB	Output is correct
13	Correct	1 ms	364 KB	Output is correct
14	Correct	2 ms	364 KB	Output is correct
15	Correct	1 ms	364 KB	Output is correct
16	Correct	1 ms	364 KB	Output is correct
17	Correct	1 ms	364 KB	Output is correct
18	Correct	1 ms	364 KB	Output is correct
19	Correct	1 ms	364 KB	Output is correct
20	Correct	1 ms	364 KB	Output is correct
21	Correct	1 ms	364 KB	Output is correct
22	Correct	1 ms	364 KB	Output is correct
23	Correct	1 ms	364 KB	Output is correct
24	Correct	2 ms	364 KB	Output is correct
25	Correct	1 ms	364 KB	Output is correct
26	Correct	2 ms	364 KB	Output is correct
27	Correct	2 ms	364 KB	Output is correct
28	Correct	2 ms	364 KB	Output is correct
29	Correct	2 ms	364 KB	Output is correct
30	Correct	2 ms	364 KB	Output is correct
31	Correct	2 ms	436 KB	Output is correct
32	Correct	2 ms	364 KB	Output is correct
33	Correct	18 ms	1632 KB	Output is correct
34	Correct	19 ms	1612 KB	Output is correct
35	Correct	96 ms	1616 KB	Output is correct
36	Correct	23 ms	1996 KB	Output is correct
37	Correct	25 ms	1996 KB	Output is correct
38	Correct	126 ms	2000 KB	Output is correct
39	Correct	29 ms	2436 KB	Output is correct
40	Correct	31 ms	2560 KB	Output is correct
41	Correct	172 ms	2528 KB	Output is correct
42	Correct	37 ms	2932 KB	Output is correct
43	Correct	40 ms	2956 KB	Output is correct
44	Correct	212 ms	2900 KB	Output is correct
45	Correct	43 ms	3452 KB	Output is correct
46	Correct	44 ms	3404 KB	Output is correct
47	Correct	247 ms	3564 KB	Output is correct
48	Correct	54 ms	3964 KB	Output is correct
49	Correct	53 ms	3964 KB	Output is correct
50	Correct	298 ms	3980 KB	Output is correct
51	Correct	60 ms	4712 KB	Output is correct
52	Correct	62 ms	4632 KB	Output is correct
53	Correct	364 ms	4700 KB	Output is correct
54	Correct	72 ms	5324 KB	Output is correct
55	Correct	72 ms	5292 KB	Output is correct
56	Correct	476 ms	5420 KB	Output is correct
57	Correct	83 ms	6012 KB	Output is correct
58	Correct	88 ms	6012 KB	Output is correct
59	Correct	527 ms	6080 KB	Output is correct
60	Correct	95 ms	6944 KB	Output is correct
61	Correct	93 ms	6816 KB	Output is correct
62	Correct	579 ms	6884 KB	Output is correct
63	Correct	354 ms	6920 KB	Output is correct
64	Correct	632 ms	6884 KB	Output is correct
65	Correct	490 ms	6916 KB	Output is correct
66	Correct	403 ms	6868 KB	Output is correct
67	Correct	387 ms	6772 KB	Output is correct
68	Correct	190 ms	6796 KB	Output is correct
69	Correct	170 ms	6860 KB	Output is correct
70	Correct	134 ms	6780 KB	Output is correct
71	Correct	146 ms	6796 KB	Output is correct
72	Correct	111 ms	6764 KB	Output is correct
73	Correct	148 ms	6788 KB	Output is correct
74	Correct	276 ms	6788 KB	Output is correct
75	Correct	327 ms	7008 KB	Output is correct
76	Correct	285 ms	6788 KB	Output is correct
77	Correct	288 ms	6892 KB	Output is correct
78	Correct	355 ms	6892 KB	Output is correct
79	Correct	226 ms	6904 KB	Output is correct
80	Correct	279 ms	6792 KB	Output is correct
81	Correct	318 ms	6904 KB	Output is correct
82	Correct	281 ms	6784 KB	Output is correct
83	Correct	377 ms	6864 KB	Output is correct
84	Correct	336 ms	6912 KB	Output is correct
85	Correct	371 ms	6812 KB	Output is correct
86	Correct	363 ms	6940 KB	Output is correct
87	Correct	360 ms	6780 KB	Output is correct
88	Correct	389 ms	6928 KB	Output is correct
89	Correct	390 ms	6784 KB	Output is correct
90	Correct	411 ms	6892 KB	Output is correct
91	Correct	396 ms	6840 KB	Output is correct
92	Correct	422 ms	6904 KB	Output is correct