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Submission #168962

# Submission time Handle Problem Language Result Execution time Memory
168962 2019-12-17T10:05:12 Z dolphingarlic Mecho (IOI09_mecho) C++14
100 / 100
 299 ms 22520 KB 
#include <bits/stdc++.h>
#pragma GCC Optimize("O3")
using namespace std;

#define MAX_N 2000

int cx[4] = {1, -1, 0, 0};
int cy[4] = {0, 0, 1, -1};

char mainMap[MAX_N][MAX_N];
bool reachable[MAX_N][MAX_N];

// The time that it takes the bees to reach any cell in the map
int beeDistance[MAX_N][MAX_N];

int n, s;
int dx, dy;
int mx, my;

/**
 * Tests if Mecho is able to reach his home after staying with
 * the honey for the given delay time.
 */
bool test(int delay) {
    // Check if the bees catch Mecho whilst he is still with
    // the honey.
    if (delay * s >= beeDistance[mx][my]) return false;

    memset(reachable, 0, sizeof(reachable));
    deque<pair<int, pair<int, int> > > q;
    q.push_back(make_pair(delay * s, make_pair(mx, my)));
    reachable[mx][my] = true;

    // Now do the main loop to see what other cells Mecho can reach.
    while (!q.empty()) {
        int distance = q.front().first;
        int x = q.front().second.first;
        int y = q.front().second.second;

        q.pop_front();

        // If Mecho has reached his home, then we are done.
        if (mainMap[x][y] == 'D') return true;

        // Check neighbouring cells
        for (int c = 0; c < 4; c++) {
            int nx = x + cx[c];
            int ny = y + cy[c];

            // Check that the cell is valid, that it is not a tree, and
            // that Mecho can get here before the bees.
            if (nx < 0 || nx >= n || ny < 0 || ny >= n ||
                mainMap[nx][ny] == 'T' ||
                (distance + 1) >= beeDistance[nx][ny] || reachable[nx][ny])
                continue;

            // All OK, so add it to the queue
            q.push_back(make_pair(distance + 1, make_pair(nx, ny)));
            reachable[nx][ny] = true;
        }
    }

    // If we reach here, then Mecho was unable to reach his home.
    return false;
}
int main() {
    cin >> n >> s;

    deque<pair<int, int> > bq;
    memset(beeDistance, -1, sizeof(beeDistance));

    for (int i = 0; i < n; i++) {
        cin >> ws;
        for (int j = 0; j < n; j++) {
            cin >> mainMap[i][j];
            if (mainMap[i][j] == 'H') {
                bq.push_back(make_pair(i, j));
                beeDistance[i][j] = 0;
            } else if (mainMap[i][j] == 'M') {
                mx = i;
                my = j;

                // Bees can travel through the location of the honey
                mainMap[i][j] = 'G';
            } else if (mainMap[i][j] == 'D') {
                dx = i;
                dy = j;
            }
        }
    }

    // Precompute the time that it takes the bees to reach any other
    // cell in the map.
    while (!bq.empty()) {
        int x = bq.front().first;
        int y = bq.front().second;

        bq.pop_front();

        for (int c = 0; c < 4; c++) {
            int nx = x + cx[c];
            int ny = y + cy[c];

            if (nx < 0 || nx >= n || ny < 0 || ny >= n ||
                mainMap[nx][ny] != 'G' || beeDistance[nx][ny] != -1)
                continue;

            beeDistance[nx][ny] = beeDistance[x][y] + s;
            bq.push_back(make_pair(nx, ny));
        }
    }

    // The bees can never enter Mecho's home, so set this to a large
    // sentinel value.
    beeDistance[dx][dy] = n * n * s;

    // Binary search to find the maximum delay time.
    int low = -1, high = 2 * n * n;
    while (high - low > 1) {
        int mid = (low + high) >> 1;
        if (test(mid))
            low = mid;
        else
            high = mid;
    }

    cout << low;
    return 0;
}

Compilation message

mecho.cpp:2:0: warning: ignoring #pragma GCC Optimize [-Wunknown-pragmas]
 #pragma GCC Optimize("O3")

Subtask #1
100.0 / 100.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 20088 KB Output is correct
2 Correct 22 ms 19968 KB Output is correct
3 Correct 18 ms 19832 KB Output is correct
4 Correct 24 ms 19960 KB Output is correct
5 Correct 21 ms 19960 KB Output is correct
6 Correct 19 ms 19960 KB Output is correct
7 Correct 185 ms 22364 KB Output is correct
8 Correct 18 ms 19960 KB Output is correct
9 Correct 18 ms 19960 KB Output is correct
10 Correct 19 ms 19960 KB Output is correct
11 Correct 18 ms 19960 KB Output is correct
12 Correct 19 ms 20088 KB Output is correct
13 Correct 19 ms 19948 KB Output is correct
14 Correct 20 ms 20092 KB Output is correct
15 Correct 19 ms 19960 KB Output is correct
16 Correct 19 ms 19960 KB Output is correct
17 Correct 19 ms 19960 KB Output is correct
18 Correct 19 ms 19960 KB Output is correct
19 Correct 20 ms 19960 KB Output is correct
20 Correct 19 ms 19960 KB Output is correct
21 Correct 20 ms 19960 KB Output is correct
22 Correct 20 ms 19960 KB Output is correct
23 Correct 20 ms 19960 KB Output is correct
24 Correct 19 ms 19960 KB Output is correct
25 Correct 20 ms 19960 KB Output is correct
26 Correct 20 ms 19960 KB Output is correct
27 Correct 20 ms 20088 KB Output is correct
28 Correct 20 ms 20088 KB Output is correct
29 Correct 21 ms 19960 KB Output is correct
30 Correct 20 ms 19960 KB Output is correct
31 Correct 20 ms 20088 KB Output is correct
32 Correct 21 ms 20216 KB Output is correct
33 Correct 34 ms 20728 KB Output is correct
34 Correct 35 ms 20728 KB Output is correct
35 Correct 51 ms 20728 KB Output is correct
36 Correct 38 ms 20856 KB Output is correct
37 Correct 39 ms 20856 KB Output is correct
38 Correct 63 ms 20856 KB Output is correct
39 Correct 43 ms 20984 KB Output is correct
40 Correct 43 ms 20984 KB Output is correct
41 Correct 75 ms 20984 KB Output is correct
42 Correct 48 ms 21112 KB Output is correct
43 Correct 49 ms 21112 KB Output is correct
44 Correct 88 ms 21084 KB Output is correct
45 Correct 56 ms 21240 KB Output is correct
46 Correct 54 ms 21240 KB Output is correct
47 Correct 100 ms 21240 KB Output is correct
48 Correct 64 ms 21500 KB Output is correct
49 Correct 61 ms 21468 KB Output is correct
50 Correct 153 ms 21468 KB Output is correct
51 Correct 76 ms 21624 KB Output is correct
52 Correct 70 ms 21752 KB Output is correct
53 Correct 168 ms 21672 KB Output is correct
54 Correct 78 ms 21752 KB Output is correct
55 Correct 74 ms 21752 KB Output is correct
56 Correct 176 ms 21880 KB Output is correct
57 Correct 84 ms 21916 KB Output is correct
58 Correct 84 ms 21980 KB Output is correct
59 Correct 200 ms 22008 KB Output is correct
60 Correct 91 ms 22136 KB Output is correct
61 Correct 90 ms 22072 KB Output is correct
62 Correct 221 ms 22140 KB Output is correct
63 Correct 187 ms 22136 KB Output is correct
64 Correct 299 ms 22136 KB Output is correct
65 Correct 239 ms 22140 KB Output is correct
66 Correct 212 ms 22176 KB Output is correct
67 Correct 203 ms 22136 KB Output is correct
68 Correct 126 ms 22136 KB Output is correct
69 Correct 125 ms 22108 KB Output is correct
70 Correct 112 ms 22200 KB Output is correct
71 Correct 120 ms 22064 KB Output is correct
72 Correct 105 ms 22096 KB Output is correct
73 Correct 109 ms 22364 KB Output is correct
74 Correct 136 ms 22392 KB Output is correct
75 Correct 151 ms 22388 KB Output is correct
76 Correct 139 ms 22356 KB Output is correct
77 Correct 139 ms 22520 KB Output is correct
78 Correct 156 ms 22428 KB Output is correct
79 Correct 125 ms 22336 KB Output is correct
80 Correct 136 ms 22376 KB Output is correct
81 Correct 145 ms 22392 KB Output is correct
82 Correct 138 ms 22276 KB Output is correct
83 Correct 156 ms 22324 KB Output is correct
84 Correct 176 ms 22376 KB Output is correct
85 Correct 165 ms 22308 KB Output is correct
86 Correct 163 ms 22492 KB Output is correct
87 Correct 161 ms 22288 KB Output is correct
88 Correct 167 ms 22340 KB Output is correct
89 Correct 167 ms 22236 KB Output is correct
90 Correct 173 ms 22392 KB Output is correct
91 Correct 165 ms 22264 KB Output is correct
92 Correct 173 ms 22260 KB Output is correct