hdu1180诡异的楼梯(bfs)

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题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1180
这个题真的是坑啊。。等楼梯的时候要看看对面是否已经访问过了，如果访问过了，就没有必要过楼梯了。。。。这点很重要。。。。
代码：
#include <cstdio>#include <queue>#include <cstring>using namespace std;char s[30][30];int v[30][30];int n,m;int stx,sty,endx,endy;int ans ;int dx[] = {-1,0,1,0};int dy[] = {0,1,0,-1};struct Node{    int x,y;    int time;};bool isOk(int x,int y,Node t,Node &r){    int dir;    for(int i = 0; i < 4; ++i)    {        int tx = t.x + dx[i];        int ty = t.y + dy[i];        if(tx == x && ty == y)        {            dir = i;            break;        }    }    int nextx = x + dx[dir];    int nexty = y + dy[dir];    if(nextx >= 0 && nextx < n && nexty >= 0 && nexty < m && s[nextx][nexty] != '*' && !v[nextx][nexty])    {        if(dir % 2 == 0)        {            if((s[x][y] == '|' && t.time % 2 == 0) || (s[x][y] == '-' && t.time % 2))            {                r.x = nextx;                r.y = nexty;                r.time = t.time + 1;                return true;            }            else            {                r.x = nextx;                r.y = nexty;                r.time = t.time + 2;                       //printf("flag = %d\n",flag);                return true;            }        }        else if(dir % 2)        {            if((s[x][y] == '|' && t.time % 2) || (s[x][y] == '-' && t.time % 2 == 0))            {                r.x = nextx;                r.y = nexty;                r.time = t.time + 1;                return true;            }            else            {                r.x = nextx;                r.y = nexty;                r.time = t.time + 2;                      // printf("flag = %d\n",flag);                return true;            }        }    }    return false;}void bfs(int x,int y){    queue<Node> q;    Node first;    first.x = x;    first.y = y;    first.time = 0;    q.push(first);    v[x][y] = 1;    while(!q.empty())    {        Node head = q.front();        q.pop();        for(int i = 0; i < 4; ++i)        {            int tx = head.x + dx[i];            int ty = head.y + dy[i];            if(tx == endx && ty == endy)            {                ans = head.time + 1;                return ;            }            if(tx >= 0 && tx < n && ty >= 0 && ty < m && !v[tx][ty])            {                if(s[tx][ty] == '.')                {                    Node t;                    t.x = tx;                    t.y = ty;                    t.time = head.time + 1;                    q.push(t);                    v[tx][ty] = 1;                }                else if(s[tx][ty] == '|' || s[tx][ty] =='-')                {                    Node t;                    if(isOk(tx,ty,head,t))                    {                        //printf("%d %d\n",t.x,t.y);                        if(t.x == endx && t.y == endy)                        {                            ans = t.time;                            return ;                        }                        q.push(t);                        v[t.x][t.y] = 1;                    }                }            }        }    }}int main(){    while(~scanf("%d%d",&n,&m))    {        if(!m || !n)        {            printf("0\n");            continue;        }        memset(v,0,sizeof v);        for(int i = 0; i < n; ++i)            scanf("%s",s[i]);        for(int i = 0; i < n; ++i)        {            for(int j = 0; j < m; ++j)                if(s[i][j] == 'S')                {                    stx = i;                    sty = j;                }                else if(s[i][j] == 'T')                {                    endx = i;                    endy = j;                }        }        ans = 0;        bfs(stx,sty);        printf("%d\n",ans);    }    return 0;}
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