POJ2251

POJ2251

用BFS就是增加一个维度，变成3维

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
using namespace std;
int L, R, C;
const int MAX_SIZE = 30;

int g[MAX_SIZE][MAX_SIZE][MAX_SIZE];
int vis[MAX_SIZE][MAX_SIZE][MAX_SIZE];
int star[3];
int endd[3];
int mov[6][3] = {{0,0,-1},{0,0,1},{0,-1,0},{0,1,0},{-1,0,0},{1,0,0}}; //以后方向数组都这样写

struct node
{
    int x,y,z,step;
};

int check(int x,int y,int z)
{
    if(x<0 || y<0 || z<0 || x>=L || y >= R || z >= C)
        return 1;
    if(g[x][y][z] == 1)
        return 1;
    if(vis[x][y][z] == 1)
        return 1;
    return 0;
}

int BFS()
{
    node tmp, next;
    tmp.x = star[0]; tmp.y = star[1]; tmp.z = star[2]; tmp.step = 0;
    vis[tmp.x][tmp.y][tmp.z] = 1;
    queue<node> que;
    que.push(tmp);
    vis[tmp.x][tmp.y][tmp.z] = 1;

    while(!que.empty())
    {
        tmp = que.front();
        que.pop();

        if(g[tmp.x][tmp.y][tmp.z] == 2)
            return tmp.step;

        for(int i = 0; i < 6; ++i)
        {
            next.x = tmp.x + mov[i][0];
            next.y = tmp.y + mov[i][1];
            next.z = tmp.z + mov[i][2];

            if (check(next.x, next.y, next.z))
                continue;

            next.step = tmp.step + 1;
            vis[next.x][next.y][next.z] = 1;
            que.push(next);
        }
    }
    return 0;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

    char c;
    while(cin >> L >> R >> C && L && R && C)
    {
        if(L == R && R == C && C == 0)
            break;


        memset(g, 0, sizeof(g));
        memset(vis, 0, sizeof(vis));

        for(int i = 0; i < L; ++i)
        {
            for(int j = 0; j < R; ++j)
            {
                for(int k = 0; k < C; ++k)
                {
                    cin >> c;
                    //putchar(c);
                    if(c == 'S')
                    {
                        g[i][j][k] = -1;
                        star[0] = i;
                        star[1] = j;
                        star[2] = k;
                    }
                    else if(c == '.')
                        g[i][j][k] = 0;
                    else if(c == '#')
                        g[i][j][k] = 1;
                    else if(c == 'E')
                    {
                        g[i][j][k] = 2;
                        endd[0] = i;
                        endd[1] = j;
                        endd[2] = k;
                    }
                }
            }
            if(i < L-1)
                getchar();
        }

//
//        for(int i = 0; i < L; ++i)
//        {
//            for(int j = 0; j < R; ++j)
//            {
//                for(int k = 0; k < C; ++k)
//                {
//                    printf("%d ", g[i][j][k]);
//                }
//                puts("");
//            }
//            puts("
");
//        }
//
        int rrr = BFS();

        if(rrr == 0)
            printf("Trapped!
");
        else
            printf("Escaped in %d minute(s).
", rrr);
    }

    return 0;
}

这道题用DFS写法超时，不过，在练DFS思路，就用DFS写了。

思路：将图保存下来之后，从起始点开始进行DFS，如果遇到终点就停止并返回。

我的DFS是，现在本层上进行DFS（二维），如果在本层不能找到，就从这个点调到下一维的这个点上，继续进行DFS。每次从当前点调到相邻的下一层。 

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>

using namespace std;
int L, R, C;
const int MAX_SIZE = 30;

int g[MAX_SIZE][MAX_SIZE][MAX_SIZE];
int vis[MAX_SIZE][MAX_SIZE][MAX_SIZE];
int mov_row[4] = {-1,0,0,1};
int mov_col[4] = {0,-1,1,0};
int star[] = {0,0,0};
int endd[] = {0,0,0};
int ans;
int flag = 0;

void DFS(int level, int row, int col)
{
    if(level == endd[0] && row == endd[1] && col == endd[2])
    {
        printf("Escaped in %d minute(s).
", ans);
        flag = 1;
        return;
    }

    if(level == L)
        return;

    for(int i = 0; i < 4; ++i)
    {
        int x = row+mov_row[i];
        int y = col+mov_col[i];
        if(x >= 0 && x < R && y >= 0 && y < C)
        {
            if( vis[level][x][y] == 0 && g[level][x][y] == 0 && g[level][x][y] != 2 && flag == 0)
            {
                vis[level][x][y] = 1;
                ans += 1;
                DFS(level, x, y);
                ans -= 1;
                vis[level][x][y] = 0;
            }
        }
    }

    if(flag == 0)
    {
        vis[level+1][row][col] = 1;
        ans += 1;
        DFS(level+1, row, col);
        ans -= 1;
        vis[level+1][row][col] = 0;
    }
}

int main()
{
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);

    char c;
    while(cin >> L >> R >> C && L && R && C)
    {
        if(L == R && R == C && C == 0)
            break;

        ans = 0;
        flag = 0;
        memset(g, 0, sizeof(g));
        memset(vis, 0, sizeof(vis));

        for(int i = 0; i < L; ++i)
        {
            for(int j = 0; j < R; ++j)
            {
                for(int k = 0; k < C; ++k)
                {
                    cin >> c;
                    //putchar(c);
                    if(c == 'S')
                    {
                        g[i][j][k] = -1;
                        star[0] = i;
                        star[1] = j;
                        star[2] = k;
                    }
                    else if(c == '.')
                        g[i][j][k] = 0;
                    else if(c == '#')
                        g[i][j][k] = 1;
                    else if(c == 'E')
                    {
                        g[i][j][k] = 2;
                        endd[0] = i;
                        endd[1] = j;
                        endd[2] = k;
                    }
                }
            }
            if(i < L-1)
                getchar();
        }

//        for(int i = 0; i < L; ++i)
//        {
//            for(int j = 0; j < R; ++j)
//            {
//                for(int k = 0; k < C; ++k)
//                {
//                    printf("%d ", g[i][j][k]);
//                }
//                puts("");
//            }
//            puts("
");
//        }

        vis[star[0]][star[1]][star[2]] = 1;
        DFS(star[0],star[1],star[2]);
        //cout << flag << endl;
        if(flag == 0)
            printf("Trapped!
");
    }
    return 0;
}