oj.uz

Submission #726446

# Submission time Handle Problem Language Result Execution time Memory
726446 2023-04-18T23:07:48 Z Tigerpants Portals (BOI14_portals) C++17
70 / 100
 1000 ms 99600 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 goal;
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]) {
        if (a.first == b.first) return a.second < b.second;
        return a.first < b.first;
    }
    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);
    goal.resize(R);
    dp.resize(R);
    rep(i, 0, 4) portal[i].resize(R);

    rep(i, 0, R) {
        wall[i].resize(C);
        goal[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_goal();
    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 (BFS.find(next) != BFS.end()) {
                BFS.erase(next);
                dp[next.first][next.second] = min<ll>(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 (BFS.find(next) != BFS.end()) {
                BFS.erase(next);
                dp[next.first][next.second] = min<ll>(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();
    }
}

void calc_goal() {
    vvb vis(R, vb(C, false));
    goal[cake.first][cake.second] = 0;
    vpll q;
    vpll p;
    q.pb(cake);
    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 ((!vis[next.first][next.second]) && (board[next.first][next.second])) {
                    vis[next.first][next.second] = true;
                    goal[next.first][next.second] = goal[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 1 ms 212 KB Output is correct
2 Correct 1 ms 212 KB Output is correct
3 Correct 1 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 340 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 340 KB Output is correct
8 Correct 1 ms 212 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 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 340 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 316 KB Output is correct
9 Correct 7 ms 596 KB Output is correct
10 Correct 8 ms 568 KB Output is correct
11 Correct 4 ms 468 KB Output is correct
12 Correct 4 ms 596 KB Output is correct
13 Correct 5 ms 596 KB Output is correct
14 Correct 1 ms 212 KB Output is correct
15 Correct 4 ms 596 KB Output is correct
16 Correct 1 ms 212 KB Output is correct

Subtask #3
20.0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 320 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 49 ms 4040 KB Output is correct
6 Correct 60 ms 4116 KB Output is correct
7 Correct 61 ms 4300 KB Output is correct
8 Correct 51 ms 4260 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 320 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 320 KB Output is correct
6 Correct 1 ms 340 KB Output is correct
7 Correct 1 ms 340 KB Output is correct
8 Correct 1 ms 340 KB Output is correct
9 Correct 6 ms 596 KB Output is correct
10 Correct 9 ms 596 KB Output is correct
11 Correct 3 ms 580 KB Output is correct
12 Correct 4 ms 596 KB Output is correct
13 Correct 4 ms 596 KB Output is correct
14 Correct 51 ms 4092 KB Output is correct
15 Correct 57 ms 4072 KB Output is correct
16 Correct 60 ms 4304 KB Output is correct
17 Correct 65 ms 4184 KB Output is correct
18 Correct 100 ms 4620 KB Output is correct
19 Correct 96 ms 5164 KB Output is correct
20 Correct 120 ms 5148 KB Output is correct
21 Correct 50 ms 4124 KB Output is correct
22 Correct 54 ms 4044 KB Output is correct
23 Correct 59 ms 4200 KB Output is correct
24 Correct 84 ms 5196 KB Output is correct
25 Correct 1 ms 212 KB Output is correct
26 Correct 4 ms 596 KB Output is correct
27 Correct 1 ms 212 KB Output is correct
28 Correct 48 ms 4328 KB Output is correct

Subtask #5
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 1 ms 320 KB Output is correct
3 Correct 1 ms 212 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 340 KB Output is correct
6 Correct 1 ms 316 KB Output is correct
7 Correct 1 ms 320 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 5 ms 596 KB Output is correct
10 Correct 7 ms 576 KB Output is correct
11 Correct 3 ms 468 KB Output is correct
12 Correct 3 ms 468 KB Output is correct
13 Correct 4 ms 600 KB Output is correct
14 Correct 51 ms 4112 KB Output is correct
15 Correct 59 ms 4160 KB Output is correct
16 Correct 65 ms 4304 KB Output is correct
17 Correct 61 ms 4260 KB Output is correct
18 Correct 79 ms 4540 KB Output is correct
19 Correct 91 ms 5160 KB Output is correct
20 Correct 136 ms 5068 KB Output is correct
21 Correct 51 ms 4124 KB Output is correct
22 Correct 55 ms 4140 KB Output is correct
23 Correct 54 ms 4204 KB Output is correct
24 Execution timed out 1086 ms 99600 KB Time limit exceeded
25 Halted 0 ms 0 KB -