Tunnels HDU - 4856

BFS寻找每个点到其他点的最小距离

再状压DP，DP[i][j] i二进制表示每个点的到达状态，j为当前所在点

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
#define pii pair<int,int>
#define CLR(a,b) memset(a,b,sizeof(a))
const int INF = 0x3f3f3f3f;
const int maxn = 40000;
char maze[20][20];
int vis[20][20];
int dis[20][20][20][20];
int dx[4] = {1,-1,0,0};
int dy[4] = {0,0,1,-1};
int n,m;

int Dis[20][20][20][20];

struct Node{
    int x,y;
    int d;
    Node(int x,int y,int d){
        this->x = x;
        this->y = y;
        this->d = d;
    }
};
queue<Node> Queue;

void bfs(int x,int y)
{
    vis[x][y] = 1;
    dis[x][y][x][y] = 0;
    Queue.push(Node(x,y,0));
    while(Queue.size()){
        int nx = Queue.front().x;
        int ny = Queue.front().y;
        int nd = Queue.front().d;
        Queue.pop();
        for(int i=0;i<4;i++){
            if(nx + dx[i] >=1 && nx + dx[i] <=n && ny + dy[i] >=1 && ny + dy[i] <= n){
                if(!vis[nx + dx[i]][ny + dy[i]] && maze[nx + dx[i]][ny + dy[i]] == '.'){
                    dis[x][y][nx + dx[i]][ny + dy[i]] = nd + 1;
                    vis[nx + dx[i]][ny + dy[i]] = 1;
                    Queue.push(Node(nx + dx[i],ny + dy[i],nd + 1));
                }
            }
        }
    }
}

int dp[maxn][20];
int POW[20];
int mm[20][5];
int flag = 0;

void solve()
{
    POW[0] = 1;
    for(int i=1;i<20;i++){
        POW[i] = POW[i-1]*2;
    }

    CLR(dp,0x3f);
    for(int i=0;i<m;i++)
        dp[1<<i][i] = 0;

    for(int i=1;i<POW[m];i++){
        for(int j=0;j<m;j++){
            if((i&POW[j]) == POW[j]){

                int n = i^POW[j];
                for(int k=0;k<m;k++){
                    if( (n&POW[k]) == POW[k]){
                        int a = mm[k][3];
                        int b = mm[k][4];
                        int aa = mm[j][1];
                        int bb = mm[j][2];

                        dp[i][j] = min(dp[n][k] + dis[a][b][aa][bb],dp[i][j]);
 //                       cout<<dp[i][j]<<endl;
                    }
                }
            }
        }
    }

}

int main()
{
//    freopen("in.txt","r",stdin);
    while(cin>>n>>m){
        for(int i=1;i<=n;i++){
            scanf("%s",maze[i]+1);
        }
        for(int i=0;i<20;i++) for(int j=0;j<20;j++) for(int k=0;k<20;k++) for(int l=0;l<20;l++) dis[i][j][k][l] = INF;
        for(int i=1;i<=n;i++){
            for(int j=1;j<=n;j++){
                if(maze[i][j] == '.'){
                    CLR(vis,0);
                    bfs(i,j);
                }
            }
        }
        for(int i=0;i<m;i++){
            cin>>mm[i][1]>>mm[i][2]>>mm[i][3]>>mm[i][4];
        }
        solve();
        int ans = INF;
        for(int i=0;i<m;i++){
            ans = min(dp[POW[m]-1][i],ans);
        }
        if(ans == INF){
            cout<<-1<<endl;
        }
        else
            cout<<ans<<endl;
    }
    return 0;
}