hdu4771 Stealing Harry Potter's Precious(DFS,BFS)

练习dfs和bfs的好题。

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<algorithm>
#include<stack>
#include<queue>
#include<cctype>
#include<sstream>
using namespace std;
#define pii pair<int,int>
#define LL long long int
const int eps=1e-8;
const int INF=1000000000;
const int maxnm=100+10;
int ans,n,m,k,d[5][5];
int dx[4]= {1,-1,0,0};
int dy[4]= {0,0,1,-1};
char maps[maxnm][maxnm];
int had[maxnm][maxnm];
struct Precious
{
    int x,y;
    bool used;
} p[5];
int Bfs(int from,int to);
bool Dfs(int id,int now,int step);
void ini();
int main()
{
    //freopen("in8.txt","r",stdin);
    while(scanf("%d%d",&n,&m)==2)
    {
        if(n==0&&m==0) break;
        ini();
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=m; j++)
            {
                cin>>maps[i][j];
                if(maps[i][j]=='@')
                {
                    p[0].x=i;
                    p[0].y=j;
                }
            }
        }
        scanf("%d",&k);
        for(int i=1; i<=k; i++)
        {
            int xx,yy;
            scanf("%d%d",&xx,&yy);
            p[i].x=xx;
            p[i].y=yy;
        }
        if(Dfs(0,0,0))
        {
            printf("%d
",ans);
        }
        else
        {
            printf("-1
");
        }
    }
    return 0;
}
void ini()
{
    memset(d,-1,sizeof(d));
    ans=INF;
    for(int i=0; i<5; i++)
    {
        p[i].used=0;
    }
}
int Bfs(int from,int to)
{
    if(d[from][to]!=-1) return d[from][to];
    if((p[from].x==p[to].x)&&(p[from].y==p[to].y))
    {
        return d[from][to]=0;
    }
    else
    {
        queue<pii>q;
        memset(had,0,sizeof(had));
        q.push(make_pair(p[from].x,p[from].y));
        had[p[from].x][p[from].y]=1;
        while(!q.empty())
        {
            int tx=q.front().first;
            int ty=q.front().second;
            q.pop();
            for(int i=0; i<4; i++)
            {
                int X=tx+dx[i];
                int Y=ty+dy[i];
                if(X>=1&&X<=n&&Y>=1&&Y<=m)
                {
                    if(had[X][Y]||maps[X][Y]=='#')
                    {
                        continue;
                    }
                    else
                    {
                        q.push(make_pair(X,Y));
                        had[X][Y]=had[tx][ty]+1;
                        if(X==p[to].x&&Y==p[to].y)
                        {
                            return d[from][to]=had[X][Y]-1;
                        }
                    }
                }
            }
        }
        return d[from][to]=-2;
    }
}

bool Dfs(int id,int now,int step)
//id表示现在在哪点，now表示已经拿了几个，step表示目前一共走了几步
{
    bool w=0;
    p[id].used=1;
    if(now==k)
    {
        //cout<<"***"<<step<<endl;
        ans=min(ans,step);
        p[id].used=0;
        return true;
    }
    else
    {
        for(int i=1; i<=k; i++)
        {
            if(p[i].used==0)
            {
                int stt=Bfs(id,i);
                if(stt==-2)
                {
                    p[id].used=0;
                    return false;
                }
                else
                {
                    if(Dfs(i,now+1,step+stt))
                    {
                        w=1;
                    }
                }
            }
        }
        if(w==1)
        {
            p[id].used=0;
            return true;
        }
        else
        {
            p[id].used=0;
            return false;
        }
    }
}