oj.uz

Submission #726449

# Submission time Handle Problem Language Result Execution time Memory
726449 2023-04-18T23:38:38 Z Tigerpants Portals (BOI14_portals) C++17
70 / 100
 1000 ms 90736 KB 
#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <numeric>
#include <functional>
#include <queue>

using namespace std;

typedef long long int ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;


#define rep(i, a, b) for (ll i = a; i < b; i++)
#define mp(a, b) make_pair(a, b)
#define sz(a) a.size()
#define pb(a) push_back(a)

const ll INF = 1000000000;

vvll wall;
vvll dp;
vvll portal[4]; // for each of the 4 directions, get the distance to the wall...

pll start;
pll cake;
ll R, C;
vvb board;

ll dx[4] = {1, 0, -1, 0};
ll dy[4] = {0, 1, 0, -1};

void calc_wall();
void calc_goal();
void calc_portal();

bool dp_compare(pll a, pll b) {
    if (dp[a.first][a.second] == dp[b.first][b.second]) {
        return a < b;
    }
    return dp[a.first][a.second] < dp[b.first][b.second];
}
set<pll, decltype(dp_compare)*> BFS(dp_compare);

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> R >> C;
    board.resize(R + 2);
    char tmp;
    board[0].resize(C + 2);
    board[R + 1].resize(C + 2);
    rep(j, 0, C + 2) {board[0][j] = false; board[R + 1][j] = false;}
    rep(i, 1, R + 1) {
        board[i].resize(C + 2);
        board[i][0] = false;
        board[i][C + 1] = false;
        rep(j, 1, C + 1) {
            cin >> tmp;
            board[i][j] = (tmp != '#');
            if (tmp == 'S') {
                start = mp(i, j);
            }
            if (tmp == 'C') {
                cake = mp(i, j);
            }
        }
    }
    R += 2;
    C += 2;

    wall.resize(R);
    dp.resize(R);
    rep(i, 0, 4) portal[i].resize(R);

    rep(i, 0, R) {
        wall[i].resize(C);
        dp[i].resize(C);
        rep(j, 0, 4) portal[j][i].resize(C);
        rep(j, 0, C) dp[i][j] = INF;
    }

    // calculate supporting values
    calc_wall();
    calc_portal();

    // do BFS in dp graph...
    dp[start.first][start.second] = 0;

    rep(i, 0, R) {
        rep(j, 0, C) {
            if (board[i][j]) BFS.insert(mp(i, j));
        }
    }

    while (!BFS.empty()) {
        pll pos = *BFS.begin();
        BFS.erase(BFS.begin());
        
        rep(k, 0, 4) {
            // try walking
            pll next = mp(pos.first + dx[k], pos.second + dy[k]);
            if ((board[next.first][next.second]) && (dp[next.first][next.second] > dp[pos.first][pos.second] + 1)) {
                BFS.erase(next);
                dp[next.first][next.second] = dp[pos.first][pos.second] + 1;
                BFS.insert(next);
            }

            // try shooting
            next = mp(pos.first + (dx[k] * portal[k][pos.first][pos.second]), pos.second + (dy[k] * portal[k][pos.first][pos.second]));
            if ((portal[k][pos.first][pos.second] >= 1) && (dp[next.first][next.second] > dp[pos.first][pos.second] + wall[pos.first][pos.second])) {
                BFS.erase(next);
                dp[next.first][next.second] = dp[pos.first][pos.second] + wall[pos.first][pos.second];
                BFS.insert(next);
            }
        }
    }

    cout << dp[cake.first][cake.second] << endl;

    return 0;
}

void calc_wall() {
    vvb vis(R, vb(C, false));
    vpll p, q;
    rep(i, 0, R) {
        rep(j, 0, C) {
            if (!board[i][j]) {
                q.pb(mp(i, j));
                wall[i][j] = 0;
                vis[i][j] = true;
            }
        }
    }
    while (!q.empty()) {
        for (vpll::iterator itr = q.begin(); itr != q.end(); itr++) {
            rep(d, 0, 4) {
                pll next = mp(itr->first + dx[d], itr->second + dy[d]);
                if ((next.first == -1) || (next.second == -1) || (next.first == R) || (next.second == C)) continue;
                if (!vis[next.first][next.second]) {
                    vis[next.first][next.second] = true;
                    wall[next.first][next.second] = wall[itr->first][itr->second] + 1;
                    p.pb(next);
                }
            }
        }
        swap(p, q);
        p.clear();
    }
}

ll portal_dp(ll i, ll j, ll k) {
    if (portal[k][i][j] == -2) portal[k][i][j] = portal_dp(i + dx[k], j + dy[k], k) + 1;
    return portal[k][i][j];
}

void calc_portal() {
    // setup before call dp
    rep(i, 0, R) {
        rep(j, 0, C) {
            rep(k, 0, 4) {
                portal[k][i][j] = -1 -(board[i][j]);
            }
        }
    }

    rep(i, 0, R) {
        rep(j, 0, C) {
            rep(k, 0, 4) {
                portal_dp(i, j, k);
            }
        }
    }
}

// There is a (RC)^3 dp
// There is also a (RC)^2 dp: if there are 2 portals then one should b-line to one of them

// For each cell we define the following distances:
// Distance to cell before nearest wall
// Distance to goal
// Then from each cell we can do one of 3 operations:
// Move a step up/down/left/right
// Shoot a portal to a wall up/down/left/right and go to nearest wall to appear at where we shot
// Move to goal
// This gives us a 9*RC dp with RC statest and 9 edges per state...

Subtask #1
11.0 / 11.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 340 KB Output is correct
9 Correct 1 ms 212 KB Output is correct
10 Correct 1 ms 212 KB Output is correct

Subtask #2
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 0 ms 212 KB Output is correct
5 Correct 0 ms 212 KB Output is correct
6 Correct 0 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 2 ms 596 KB Output is correct
10 Correct 3 ms 596 KB Output is correct
11 Correct 2 ms 468 KB Output is correct
12 Correct 3 ms 564 KB Output is correct
13 Correct 3 ms 468 KB Output is correct
14 Correct 0 ms 212 KB Output is correct
15 Correct 2 ms 468 KB Output is correct
16 Correct 0 ms 212 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 27 ms 3772 KB Output is correct
6 Correct 28 ms 3708 KB Output is correct
7 Correct 29 ms 3872 KB Output is correct
8 Correct 27 ms 3972 KB Output is correct

Subtask #4
19.0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 1 ms 340 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 0 ms 212 KB Output is correct
8 Correct 1 ms 340 KB Output is correct
9 Correct 2 ms 596 KB Output is correct
10 Correct 2 ms 596 KB Output is correct
11 Correct 2 ms 468 KB Output is correct
12 Correct 3 ms 468 KB Output is correct
13 Correct 2 ms 468 KB Output is correct
14 Correct 27 ms 3664 KB Output is correct
15 Correct 31 ms 3816 KB Output is correct
16 Correct 31 ms 3916 KB Output is correct
17 Correct 27 ms 3872 KB Output is correct
18 Correct 33 ms 4232 KB Output is correct
19 Correct 44 ms 4876 KB Output is correct
20 Correct 42 ms 4704 KB Output is correct
21 Correct 25 ms 3776 KB Output is correct
22 Correct 27 ms 3744 KB Output is correct
23 Correct 28 ms 3800 KB Output is correct
24 Correct 39 ms 4784 KB Output is correct
25 Correct 0 ms 212 KB Output is correct
26 Correct 2 ms 468 KB Output is correct
27 Correct 1 ms 212 KB Output is correct
28 Correct 26 ms 3884 KB Output is correct

Subtask #5
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 0 ms 212 KB Output is correct
4 Correct 0 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 0 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 0 ms 340 KB Output is correct
9 Correct 3 ms 596 KB Output is correct
10 Correct 3 ms 596 KB Output is correct
11 Correct 2 ms 468 KB Output is correct
12 Correct 2 ms 468 KB Output is correct
13 Correct 2 ms 468 KB Output is correct
14 Correct 28 ms 3748 KB Output is correct
15 Correct 28 ms 3724 KB Output is correct
16 Correct 30 ms 3916 KB Output is correct
17 Correct 27 ms 3836 KB Output is correct
18 Correct 35 ms 4232 KB Output is correct
19 Correct 47 ms 4788 KB Output is correct
20 Correct 50 ms 4696 KB Output is correct
21 Correct 27 ms 3764 KB Output is correct
22 Correct 27 ms 3796 KB Output is correct
23 Correct 29 ms 3872 KB Output is correct
24 Execution timed out 1082 ms 90736 KB Time limit exceeded
25 Halted 0 ms 0 KB -