oj.uz

Submission #395797

# Submission time Handle Problem Language Result Execution time Memory
395797 2021-04-28T23:48:48 Z SirCovidThe19th Mecho (IOI09_mecho) C++14
100 / 100
 264 ms 6376 KB 
#include <bits/stdc++.h>
using namespace std;

int n, s;
int dx[4] = {1, -1, 0, 0}; int dy[4] = {0, 0, -1, 1};
int hiveDist[800][800];
char grid[800][800];

pair<int, int> start;
pair<int, int> dest;
vector<pair<int, int>> hives;

bool inside(int x, int y){
    return x >= 0 and x < n and y >= 0 and y < n;
}
//precompute how far every cell is to the nearest hive
void bees(){
    queue<pair<int, int>> trav;
    fill(&hiveDist[0][0], &hiveDist[0][0]+sizeof(hiveDist)/sizeof(hiveDist[0][0]), -1);
    for (pair<int, int> loc : hives){
        trav.push(loc); 
        hiveDist[loc.first][loc.second] = 0;
    }
    while (!trav.empty()){
        pair<int, int> curr = trav.front(); trav.pop();
        for (int i = 0; i < 4; i++){
            int x = curr.first+dx[i]; int y = curr.second+dy[i];
            if (inside(x, y) and (grid[x][y] == 'G' or grid[x][y] == 'M') and hiveDist[x][y] == -1){
                hiveDist[x][y] = hiveDist[curr.first][curr.second]+1;
                trav.push({x, y});
            }
        }
    }
}
bool bear(int wait){
    queue<pair<int, int>> trav;
    //time it takes for bees is floor(bearDist/s)
    int bearDist[n][n];
    fill(&bearDist[0][0], &bearDist[0][0]+sizeof(bearDist)/sizeof(bearDist[0][0]), -1);
    trav.push(start); bearDist[start.first][start.second] = wait*s;
    //check if bees can reach mecho before he even moves
    int hiveToStart = hiveDist[start.first][start.second];
    if (wait >= hiveToStart and hiveToStart != -1) return false;
    while (!trav.empty()){
        pair<int, int> curr = trav.front(); trav.pop();
        //smoll bfs on reachable positions
        queue<pair<int, int>> pos; pos.push(curr);
        while (!pos.empty()){
            pair<int, int> loc = pos.front(); pos.pop();
            for (int i = 0; i < 4; i++){
                int x = loc.first+dx[i]; int y = loc.second+dy[i];
                if (inside(x, y) and (grid[x][y] == 'G' or grid[x][y] == 'D') and bearDist[x][y] == -1){
                    bearDist[x][y] = bearDist[loc.first][loc.second]+1;
                    //ok, mecho reached home
                    if (grid[x][y] == 'D') return true;
                    //uh oh, bees can reach here before you can
                    if (floor(bearDist[x][y]/s) >= hiveDist[x][y] and hiveDist[x][y] != -1) continue;
                    //max distance reached
                    int maxDist = (bearDist[curr.first][curr.second]/s)+1;
                    if (bearDist[x][y] == maxDist)
                        trav.push({x, y});
                    else
                        pos.push({x, y});
                }
            }
        }
    }
    return false;
}
int main() {
    cin >> n >> s;
    for (int i = 0; i < n; i++){
        for (int j = 0; j < n; j++){
            cin >> grid[i][j];
            if (grid[i][j] == 'M') start = {i, j};
            if (grid[i][j] == 'D') dest = {i, j};
            if (grid[i][j] == 'H') hives.push_back({i, j});
        }
    }
    bees();
    //impossible
    if (!bear(0)){
        cout<<-1; return 0;
    }
    int high = n*n; int low = 0; int ans;
    while (low < high){
        int mid = (low+high)/2;
        if (bear(mid)){
            ans = mid; low = mid+1;
        }
        else 
            high = mid;
    }
    cout<<ans;
}

Compilation message

mecho.cpp: In function 'int main()':
mecho.cpp:94:11: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   94 |     cout<<ans;
      |           ^~~

Subtask #1
100.0 / 100.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2764 KB Output is correct
2 Correct 2 ms 2764 KB Output is correct
3 Correct 3 ms 2764 KB Output is correct
4 Correct 2 ms 2764 KB Output is correct
5 Correct 2 ms 2764 KB Output is correct
6 Correct 2 ms 2764 KB Output is correct
7 Correct 164 ms 6048 KB Output is correct
8 Correct 2 ms 2768 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 2 ms 2764 KB Output is correct
11 Correct 2 ms 2764 KB Output is correct
12 Correct 2 ms 2764 KB Output is correct
13 Correct 2 ms 2764 KB Output is correct
14 Correct 3 ms 2764 KB Output is correct
15 Correct 2 ms 2764 KB Output is correct
16 Correct 2 ms 2764 KB Output is correct
17 Correct 2 ms 2764 KB Output is correct
18 Correct 2 ms 2764 KB Output is correct
19 Correct 2 ms 2764 KB Output is correct
20 Correct 2 ms 2764 KB Output is correct
21 Correct 2 ms 2764 KB Output is correct
22 Correct 2 ms 2764 KB Output is correct
23 Correct 2 ms 2764 KB Output is correct
24 Correct 2 ms 2764 KB Output is correct
25 Correct 2 ms 2764 KB Output is correct
26 Correct 3 ms 2764 KB Output is correct
27 Correct 2 ms 2764 KB Output is correct
28 Correct 2 ms 2764 KB Output is correct
29 Correct 2 ms 2764 KB Output is correct
30 Correct 2 ms 2764 KB Output is correct
31 Correct 3 ms 2764 KB Output is correct
32 Correct 3 ms 2764 KB Output is correct
33 Correct 14 ms 3460 KB Output is correct
34 Correct 12 ms 3532 KB Output is correct
35 Correct 36 ms 3540 KB Output is correct
36 Correct 15 ms 3632 KB Output is correct
37 Correct 16 ms 3748 KB Output is correct
38 Correct 51 ms 3636 KB Output is correct
39 Correct 19 ms 3916 KB Output is correct
40 Correct 19 ms 3916 KB Output is correct
41 Correct 66 ms 3916 KB Output is correct
42 Correct 28 ms 4172 KB Output is correct
43 Correct 23 ms 4112 KB Output is correct
44 Correct 77 ms 4172 KB Output is correct
45 Correct 27 ms 4300 KB Output is correct
46 Correct 27 ms 4316 KB Output is correct
47 Correct 97 ms 4336 KB Output is correct
48 Correct 32 ms 4548 KB Output is correct
49 Correct 34 ms 4548 KB Output is correct
50 Correct 101 ms 4684 KB Output is correct
51 Correct 42 ms 4896 KB Output is correct
52 Correct 37 ms 4916 KB Output is correct
53 Correct 130 ms 4968 KB Output is correct
54 Correct 42 ms 5200 KB Output is correct
55 Correct 42 ms 5228 KB Output is correct
56 Correct 184 ms 5224 KB Output is correct
57 Correct 53 ms 5568 KB Output is correct
58 Correct 48 ms 5464 KB Output is correct
59 Correct 182 ms 5540 KB Output is correct
60 Correct 54 ms 5828 KB Output is correct
61 Correct 58 ms 5904 KB Output is correct
62 Correct 219 ms 5912 KB Output is correct
63 Correct 191 ms 5944 KB Output is correct
64 Correct 264 ms 5932 KB Output is correct
65 Correct 256 ms 5916 KB Output is correct
66 Correct 212 ms 6088 KB Output is correct
67 Correct 72 ms 5804 KB Output is correct
68 Correct 101 ms 5916 KB Output is correct
69 Correct 95 ms 5904 KB Output is correct
70 Correct 86 ms 5828 KB Output is correct
71 Correct 83 ms 5928 KB Output is correct
72 Correct 90 ms 5892 KB Output is correct
73 Correct 85 ms 6148 KB Output is correct
74 Correct 127 ms 6112 KB Output is correct
75 Correct 126 ms 6212 KB Output is correct
76 Correct 122 ms 6376 KB Output is correct
77 Correct 130 ms 6212 KB Output is correct
78 Correct 72 ms 6112 KB Output is correct
79 Correct 115 ms 6084 KB Output is correct
80 Correct 123 ms 6084 KB Output is correct
81 Correct 169 ms 6080 KB Output is correct
82 Correct 123 ms 6180 KB Output is correct
83 Correct 156 ms 6220 KB Output is correct
84 Correct 147 ms 6144 KB Output is correct
85 Correct 134 ms 6056 KB Output is correct
86 Correct 143 ms 6084 KB Output is correct
87 Correct 155 ms 6112 KB Output is correct
88 Correct 159 ms 5988 KB Output is correct
89 Correct 161 ms 6036 KB Output is correct
90 Correct 154 ms 6088 KB Output is correct
91 Correct 167 ms 6128 KB Output is correct
92 Correct 152 ms 6100 KB Output is correct