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c_cpp
a month ago
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Never
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 1005;
const int INF = 2e9;
int n, m;
char mat[maxn][maxn];
bool visited[maxn][maxn];
const int di[] = {-1, 1, 0, 0};
const int dj[] = {0, 0, -1, 1};
int bfs_basic(int si, int sj, int ei, int ej) {
    queue<int> q;
    q.push(si);
    q.push(sj);
    q.push(0);
    for(int i = 0; i < maxn; i++) {
        for(int j = 0; j < maxn; j++) {
            visited[i][j] = false;
        }
    }
    visited[si][sj] = true;
    while(!q.empty()) {
        int ci = q.front(); q.pop();
        int cj = q.front(); q.pop();
        int cekor = q.front(); q.pop();
        if(ci == ei and cj == ej) {
            return cekor;
        }
        for(int i = 0; i < 4; i++) {
            int ti = ci + di[i];
            int tj = cj + dj[i];
            if(ti >= 0 and ti < n and tj >= 0 and tj < m and !visited[ti][tj] and mat[ti][tj] != '#') {
                q.push(ti);
                q.push(tj);
                q.push(cekor + 1);
                visited[ti][tj] = true;
            }
        }
        
    }
    return -1;
}
int s_dist[maxn][maxn];
void bfs_S(int si, int sj) {
    
    queue<int> q;
    q.push(si);
    q.push(sj);
    q.push(0);
    for(int i = 0; i < maxn; i++) {
        for(int j = 0; j < maxn; j++) {
            visited[i][j] = false;
        }
    }
    visited[si][sj] = true;
    while(!q.empty()) {
        int ci = q.front(); q.pop();
        int cj = q.front(); q.pop();
        int cekor = q.front(); q.pop();
        
        for(int i = 0; i < 4; i++) {
            int ti = ci + di[i];
            int tj = cj + dj[i];
            if(ti >= 0 and ti < n and tj >= 0 and tj < m and !visited[ti][tj]) {
                if(mat[ti][tj] == '#') {
                    s_dist[ti][tj] = cekor + 1;
                }
                else {
                    q.push(ti);
                    q.push(tj);
                    q.push(cekor + 1);
                }
                visited[ti][tj] = true;
            }
        }
    }
}
int e_dist[maxn][maxn];
void bfs_e(int si, int sj) {
    queue<int> q;
    q.push(si);
    q.push(sj);
    q.push(0);
    for(int i = 0; i < maxn; i++) {
        for(int j = 0; j < maxn; j++) {
            visited[i][j] = false;
        }
    }
    visited[si][sj] = true;
    while(!q.empty()) {
        int ci = q.front(); q.pop();
        int cj = q.front(); q.pop();
        int cekor = q.front(); q.pop();
        
        for(int i = 0; i < 4; i++) {
            int ti = ci + di[i];
            int tj = cj + dj[i];
            if(ti >= 0 and ti < n and tj >= 0 and tj < m and !visited[ti][tj]) {
                if(mat[ti][tj] == '#') {
                    e_dist[ti][tj] = cekor + 1;
                }
                else {
                    q.push(ti);
                    q.push(tj);
                    q.push(cekor + 1);
                }
                visited[ti][tj] = true;
            }
        }
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> n >> m;
    int si = 0, sj = 0, ei = 0, ej = 0;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            cin >> mat[i][j];
            if(mat[i][j] == 'S') {
                si = i;
                sj = j;
            }
            if(mat[i][j] == 'E') {
                ei = i;
                ej = j;
            }
            s_dist[i][j] = -1;
            e_dist[i][j] = -1;
        }
    }
    int tmp = bfs_basic(si, sj, ei, ej);
    if(tmp != -1) {
        cout << tmp << endl;
        return 0;
    }
    bfs_S(si, sj);
    bfs_e(ei, ej);
    int res = -1;
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(mat[i][j] == '#' and s_dist[i][j] != -1 and e_dist[i][j] != -1) {
                res = max(res, s_dist[i][j] + e_dist[i][j]);
            }
        }
    }
    cout << res << endl;
    return 0;
}


/*
 S..#E
 ###..
 #....
 .....
 
 **/
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