HDU 1044

http://acm.hdu.edu.cn/showproblem.php?pid=1044

代码题，没什么好说的，先预处理出两点间距离，然后dfs搜一下找最大值

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;
const int INF=0xfffffff;
int n,m,L,M,ans,sum;
int dis[20][20];
char mp[55][55];

struct node{
    int x,y,step,v;
}kk[20];

int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
int vis[55][55];

int bfs(node s,node t){
    memset(vis,0,sizeof(vis));
    queue <node> q;
    s.step=0;
    q.push(s);
    vis[s.x][s.y]=1;
    while(!q.empty()){
        node u=q.front();
        if(u.x==t.x && u.y==t.y)
            return u.step;
        q.pop();
        for(int i=0;i<4;i++){
            int xx=u.x+dx[i];
            int yy=u.y+dy[i];
            if(xx<0 || xx>=n || yy<0 || yy>=m)continue;
            if(mp[xx][yy]=='*')continue;
            if(!vis[xx][yy]){
                vis[xx][yy]=1;
                node next=u;
                next.step++;next.x=xx;next.y=yy;
                if(next.step<=L)q.push(next);
            }
        }
    }
    return INF;
}

int VIS[20];

void dfs(int now,int t,int v){
    if(ans==sum)return;
    if(t>L)return;
    if(now==M+1){
        ans=max(ans,v);
        return;
    }
    for(int i=1;i<=M+1;i++){
        if(VIS[i])continue;
        VIS[i]=1;
        dfs(i,t+dis[now][i],v+kk[i].v);
        VIS[i]=0;
    } 
}

int V[20];

int main(){
    int T;
    scanf("%d",&T);
    int first=1;
    for(int cas=1;cas<=T;cas++){
        scanf("%d%d%d%d",&m,&n,&L,&M);
        sum=ans=0;
        for(int i=1;i<=M;i++){
            scanf("%d",&V[i]);
            sum+=V[i];
        }
        for(int i=0;i<n;i++)
            scanf("%s",mp[i]);
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(mp[i][j]=='@'){
                    kk[0].x=i;kk[0].y=j;kk[0].v=0;
                }
                else if(mp[i][j]=='<'){
                    kk[M+1].x=i;kk[M+1].y=j;kk[M+1].v=0;
                }
                else if(mp[i][j]>='A' && mp[i][j]<='J'){
                    kk[mp[i][j]-'A'+1].x=i;kk[mp[i][j]-'A'+1].y=j;kk[mp[i][j]-'A'+1].v=V[mp[i][j]-'A'+1];
                }
            }
        }
        memset(dis,-1,sizeof(dis));
        for(int i=0;i<=M+1;i++){
            for(int j=0;j<=M+1;j++){
                if(i==j)dis[i][j]=0;
                else{
                    if(dis[i][j]==-1){
                        dis[i][j]=bfs(kk[i],kk[j]);
                        dis[j][i]=dis[i][j];
                    }
                }
            }
        }
        memset(VIS,0,sizeof(VIS));
        VIS[0]=1;
        dfs(0,0,0);
        if(first)first=0;
        else putchar('
');
        printf("Case %d:
",cas);
        if(dis[0][M+1]==INF)puts("Impossible");
        else printf("The best score is %d.
",ans);
    }
    return 0;
}