Submission #357579

#	Time	Username	Problem	Language	Result	Execution time	Memory
357579		parsabahrami	Portals (BOI14_portals)	C++17	100 / 100	860 ms	135660 KiB

portals

// Call my Name and Save me from The Dark
#include <bits/stdc++.h>
 
using namespace std;

typedef long long int ll;
typedef pair<int, int> pii;
 
#define SZ(x)                       (int) x.size()
#define F                           first
#define S                           second

const int N = 1e3 + 10, MOD = 1e9 + 7;
int R[N][N], L[N][N], U[N][N], D[N][N], A[N][N], pd[N * N], dp[N * N], M[N * N], dx[] = {0, 0, -1, 1}, dy[] = {-1, 1, 0, 0}, n, m, st, en;
vector<pii> adj[N * N]; char S[N]; queue<int> Q;

int id(int x, int y) {
    return x * (m + 1) + y;
}

inline void add_edge(int u, int v, int w) {
    adj[u].push_back({v, w});
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) {
        scanf("%s", S + 1);
        for (int j = 1; j <= m; j++) {
            if (S[j] == '#') A[i][j] = 0;
            else if (S[j] == 'S') A[i][j] = 1, st = id(i, j);
            else if (S[j] == 'C') A[i][j] = 1, en = id(i, j);
            else A[i][j] = 1;
        }
    }
    fill(dp, dp + N * N, MOD);
    fill(pd, pd + N * N, MOD);
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (!A[i][j]) continue;
            for (int d = 0; d < 4; d++) {
                int nx = i + dx[d], ny = j + dy[d];
                if (nx <= 0 || nx > n || ny <= 0 || ny > m || !A[nx][ny]) continue;
                add_edge(id(i, j), id(nx, ny), 1);
            }
            if (SZ(adj[id(i, j)]) != 4) dp[id(i, j)] = 1, Q.push(id(i, j));
        }
    }  
    while (SZ(Q)) {
        int v = Q.front(); Q.pop();
        for (pii u : adj[v]) {
            if (dp[u.F] > dp[v] + u.S) {
                dp[u.F] = dp[v] + u.S;
                Q.push(u.F);
            }
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (!A[i][j - 1]) L[i][j] = j;
            else L[i][j] = L[i][j - 1];
        }
        for (int j = m; j >= 1; j--) {
            if (!A[i][j + 1]) R[i][j] = j;
            else R[i][j] = R[i][j + 1];
        }
    }
    for (int j = 1; j <= m; j++) {
        for (int i = 1; i <= n; i++) {
            if (!A[i - 1][j]) U[i][j] = i;
            else U[i][j] = U[i - 1][j];
        }
        for (int i = n; i; i--) {
            if (!A[i + 1][j]) D[i][j] = i;
            else D[i][j] = D[i + 1][j];
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (!A[i][j]) continue;
            int v = id(i, j), l = id(i, L[i][j]), r = id(i, R[i][j]), u = id(U[i][j], j), d = id(D[i][j], j);
            add_edge(v, u, dp[v]);
            add_edge(v, l, dp[v]);
            add_edge(v, d, dp[v]);
            add_edge(v, r, dp[v]);
        }
    }
    priority_queue<pii> pq;
    pq.push({pd[st] = 0, st});
    while (SZ(pq)) {
        int v = pq.top().S; pq.pop();
        if (M[v]) continue;
        M[v] = 1;
        for (pii u : adj[v]) {
            if (pd[u.F] > pd[v] + u.S) {
                pd[u.F] = pd[v] + u.S;
                pq.push({-pd[u.F], u.F});
            }
        }
    }
    printf("%d\n", pd[en]);
    return 0;
}

Compilation message (stderr)

portals.cpp: In function 'int main()':
portals.cpp:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   26 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
portals.cpp:28:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   28 |         scanf("%s", S + 1);
      |         ~~~~~^~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 19 / 19
• Subtask 5: 30 / 30