Submission #97094

#	Time	Username	Problem	Language	Result	Execution time	Memory
97094		dalgerok	Portals (BOI14_portals)	C++14	100 / 100	398 ms	41152 KiB

portals

#include<bits/stdc++.h>
using namespace std;


const int N = 1005,
          INF = 1e9,
          dx[] = {-1, 0, 1, 0},
          dy[] = {0, -1, 0, 1};


int n, m;
char a[N][N];
int dist_to_wall[N][N], d[N][N];
int sx, sy, tx, ty;
pair < int, int > nxt[4][N][N];

inline bool is_wall(int x, int y){
    return x < 1 || x > n || y < 1 || y > m || a[x][y] == '#';
}

void walls(){
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            dist_to_wall[i][j] = INF;
        }
    }
    queue < pair < int, int > > q;
    for(int i = 0; i <= n + 1; i++){
        for(int j = 0; j <= m + 1; j++){
            if(is_wall(i, j)){
                dist_to_wall[i][j] = 0;
                q.push(make_pair(i, j));
            }
        }
    }
    while(!q.empty()){
        int x = q.front().first,
            y = q.front().second;
        q.pop();
        for(int i = 0; i < 4; i++){
            int xx = x + dx[i],
                yy = y + dy[i];
            if(is_wall(xx, yy)){
                continue;
            }
            if(dist_to_wall[xx][yy] > dist_to_wall[x][y] + 1){
                dist_to_wall[xx][yy] = dist_to_wall[x][y] + 1;
                q.push(make_pair(xx, yy));
            }
        }
    }
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> m;
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            cin >> a[i][j];
        }
    }
    walls();
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            if(j == 1 || a[i][j - 1] == '#'){
                nxt[0][i][j] = make_pair(i, j);
            }
            else{
                nxt[0][i][j] = nxt[0][i][j - 1];
            }
            if(i == 1 || a[i - 1][j] == '#'){
                nxt[1][i][j] = make_pair(i, j);
            }
            else{
                nxt[1][i][j] = nxt[1][i - 1][j];
            }
        }
    }
    for(int i = n; i >= 1; i--){
        for(int j = m; j >= 1; j--){
            if(j == m || a[i][j + 1] == '#'){
                nxt[2][i][j] = make_pair(i, j);
            }
            else{
                nxt[2][i][j] = nxt[2][i][j + 1];
            }
            if(i == n || a[i + 1][j] == '#'){
                nxt[3][i][j] = make_pair(i, j);
            }
            else{
                nxt[3][i][j] = nxt[3][i + 1][j];
            }
        }
    }
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            d[i][j] = INF;
            if(a[i][j] == 'S'){
                sx = i;
                sy = j;
            }
            else if(a[i][j] == 'C'){
                tx = i;
                ty = j;
            }
        }
    }
    /**for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            cout << dist_to_wall[i][j] << " ";
        }
        cout << "\n";
    }*/
    priority_queue < pair < int, pair < int, int > > > q;
    d[sx][sy] = 0;
    q.push(make_pair(0, make_pair(sx, sy)));
    while(!q.empty()){
        int val = -q.top().first,
            x = q.top().second.first,
            y = q.top().second.second;
        q.pop();
        if(d[x][y] < val){
            continue;
        }
        for(int i = 0; i < 4; i++){
            int xx = x + dx[i],
                yy = y + dy[i];
            if(!is_wall(xx, yy) && d[xx][yy] > d[x][y] + 1){
                d[xx][yy] = d[x][y] + 1;
                q.push(make_pair(-d[xx][yy], make_pair(xx, yy)));
            }
        }
        for(int i = 0; i < 4; i++){
            int xx = nxt[i][x][y].first,
                yy = nxt[i][x][y].second;
            if(d[xx][yy] > d[x][y] + dist_to_wall[x][y]){
                d[xx][yy] = d[x][y] + dist_to_wall[x][y];
                q.push(make_pair(-d[xx][yy], make_pair(xx, yy)));
            }
        }
    }
    cout << d[tx][ty];
}

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