hdu 1242 || zoj 1649 Rescue

直接bfs。有几个剪枝的地方。

1. 从angel的地方开始搜，一旦搜到朋友就退出
2. guard的处理，因为遇到guard，step要额外加一，所以用优先队列来记录bfs

10ms AC

最痛苦的是，本来应当1A的，但是因为忘记判EOF，结果一直TLE，我交了9次才AC，第7次发现实在不对劲，怎么算都不可能tle的，于是把过程全部注释掉上交，结果还是tle。最终发现是忘了加EOF判断。浪费了1个小时

//hdu 1242 & zoj 1649#include <iostream>#include <cstdio>#include <queue>#include <cstring>#define FOR(i,a,b) for (int i=(a);i<(b);i++)#define sf scanf#define pf printfusing namespace std;#define N 200struct node{    int x;    int y;    int step;    node(int xx,int yy,int sstep = 0):x(xx),y(yy),step(sstep){}    node(){x = 0;y = 0; step = 0;}    node(const node & rhs)    {        x = rhs.x;        y = rhs.y;        step = rhs.step;    }    bool    operator<(const node&rhs)const    {        return step>rhs.step;    }};char nodemap[N][N];bool is_used[N][N];int f_num;int mindis;priority_queue<node> bfs_next;int n,m;int f_count;node next[4];inline void setnode(node &lhs,node rhs){    lhs.x = rhs.x;    lhs.y = rhs.y;    lhs.step = rhs.step;}inline void setnode(node &lhs,int x,int y,int step = 0){    lhs.x = x;    lhs.y = y;    lhs.step = step;}inline bool checknode(node lhs){    return lhs.x>=0 && lhs.x<n && lhs.y>=0 && lhs.y<m ;}inline bool checkuse(node lhs){    return (is_used[lhs.x][lhs.y]);}inline bool bfs(node pos){    //不再访问已经搜索过的    if (!checknode(pos)) return false;    FOR(i,0,4)    {        node tmp;        tmp.x = pos.x+next[i].x;        tmp.y = pos.y+next[i].y;        if (nodemap[tmp.x][tmp.y]!='#'&&!checkuse(tmp))        {            is_used[tmp.x][tmp.y] = true;            tmp.step = pos.step+1;            if (nodemap[tmp.x][tmp.y]=='x') tmp.step++;            if (nodemap[tmp.x][tmp.y]=='r')            {                //一旦搜到朋友就退出输出                if (tmp.step<mindis) mindis = tmp.step;                return true;                f_count--;            }            bfs_next.push(tmp);        }    }    return false;}int main(){    setnode(next[0],0,1);    setnode(next[1],0,-1);    setnode(next[2],1,0);    setnode(next[3],-1,0);    while(sf("%d %d",&n,&m)!=EOF)    {        f_num = 0 ;        node target;        while(!bfs_next.empty()) bfs_next.pop();        memset(is_used,0,sizeof(is_used));        FOR(i,0,n)        {            FOR(j,0,m)            {                sf("%c",&nodemap[i][j]);                while(nodemap[i][j]=='\n'||nodemap[i][j]==' ')sf("%c",&nodemap[i][j]);                if (nodemap[i][j]=='r')                {                    f_num ++;                }                if (nodemap[i][j]=='a')                {                    target.x = i;                    target.y = j;                    target.step = 0;                    is_used[i][j] = true ;                }            }        }        mindis = 1000000;        f_count = f_num;        bfs_next.push(target);        node nextnode;        //bfs从angel处开始搜        while(!bfs_next.empty())        {            setnode(nextnode,bfs_next.top());            bfs_next.pop();            if (bfs(nextnode)) break;        }        if (mindis!=1000000)            pf("%d\n",mindis);        else pf("Poor ANGEL has to stay in the prison all his life.\n");    }    return 0;}