HDU:4771 Stealing Harry Potter's Precious

杭州现场赛的题目，虽然大神们都说水，但我感觉还是不错的，还适合我这个水平做。

用bfs求出各个宝物之间的最短距离以及和Dudely之间的距离，然后用dfs枚举Dudely访问各个宝物的顺序，最后比较出距离和的最小值即可。

 

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<queue>#define INF 2139062143#define MAXN 105using namespace std;char grid[MAXN][MAXN];int flag[MAXN][MAXN],N,M,n,ans,x[5],y[5],dis[5][5];bool used[10],vis[MAXN][MAXN];int MM[4][2]= {{1,0},{-1,0},{0,1},{0,-1}};struct Point{    int x,y,step;    Point(int a,int b,int c):x(a),y(b),step(c) {}};void bfs(int xx,int yy){    int cur=flag[xx][yy];    queue<Point> q;    memset(vis,0,sizeof(vis));    q.push(Point(xx,yy,0));    vis[xx][yy]=true;    while(!q.empty())    {        Point u=q.front();        q.pop();        for(int i=0; i<4; ++i)        {            int ta=u.x+ MM[i][0],tb=u.y+MM[i][1];            if(ta<1||tb<1||ta>N||tb>M) continue;            if(vis[ta][tb]||grid[ta][tb]=='#') continue;            vis[ta][tb]=true;            if(flag[ta][tb]!=-1)                dis[cur][flag[ta][tb]]=u.step+1;            q.push(Point(ta,tb,u.step+1));        }    }}void dfs(int now,int res,int cur){    if(cur==n)        ans=min(ans,res);    else    {        for(int i=1; i<=n; ++i)            if(!used[i]&&dis[now][i]<INF)            {                used[i]=true;                dfs(i,res+dis[now][i],cur+1);                used[i]=false;            }    }}int main(){    while(scanf("%d%d",&N,&M)&&!(!N&&!M))    {        memset(flag,-1,sizeof(flag));        memset(grid,0,sizeof(grid));        memset(used,0,sizeof(used));        memset(dis,0x7f,sizeof(dis));        for(int i=1; i<=N; ++i)            scanf("%s",grid[i]+1);        for(int i=1; i<=N; ++i)            for(int j=1; j<=M; ++j)                if(grid[i][j]=='@')                {                    x[0]=i;                    y[0]=j;                    flag[i][j]=0;                    break;                }        scanf("%d",&n);        for(int i=1; i<=n; ++i)        {            scanf("%d%d",&x[i],&y[i]);            flag[x[i]][y[i]]=i;        }        for(int i=0; i<=n; ++i)            bfs(x[i],y[i]);        ans=INF;        dfs(0,0,0);        if(ans==INF) printf("-1\n");        else            printf("%d\n",ans);    }    return 0;}