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('\n');

        printf("Case %d:\n",cas);

        if(dis[0][M+1]==INF)puts("Impossible");

        else printf("The best score is %d.\n",ans);

    }

    return 0;

}

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