poj 3026 Borg Maze

来源：互联网发布：知乎手机怎么回答编辑：程序博客网时间：2024/05/16 09:35
思路：转化为求S和所有A点的最小生成树。通过对每个A点和S点bfs建图，然后prim求MST。
#include <iostream>#include <cstring>#include <cstdio>#include <queue>using namespace std;int move[4][2]={1,0,-1,0,0,1,0,-1};int n, m, cnt, flag[55][55], vis[55][55], a[105][105], step[55][55], visited[105];char maze[55][55];struct node{int x, y;}p[105];void init(){    char str[1005];    int i, j;    cnt=0;    gets(str);    sscanf(str, "%d%d", &m, &n);    memset(a, 0, sizeof(a));    for(i=0; i<n; i++){        gets(maze[i]);        for(j=0; j<m; j++){            if(maze[i][j]=='A'||maze[i][j]=='S'){                p[cnt].x=i;p[cnt].y=j;                flag[i][j]=cnt++;            }        }    }}bool check(node pt){    if(pt.x<0||pt.y<0|pt.x>=n||pt.y>=m||vis[pt.x][pt.y]||maze[pt.x][pt.y]=='#')    return true;    return false;}void bfs(int st){    int i;    queue<node> q;    q.push(p[st]);    node head, next;    memset(vis, 0, sizeof(vis));    memset(step, 0, sizeof(step));    step[p[st].x][p[st].y]=0;    vis[p[st].x][p[st].y]=1;    while(!q.empty()){        head=q.front();        q.pop();        for(i=0; i<4; i++){            next.x=head.x+move[i][0];            next.y=head.y+move[i][1];            if(check(next))continue;            step[next.x][next.y]=step[head.x][head.y]+1;            if(maze[next.x][next.y]=='A'||maze[next.x][next.y]=='S')                a[st][flag[next.x][next.y]]=step[next.x][next.y];            q.push(next);            vis[next.x][next.y]=1;        }    }}int prim(){    memset(visited, 0, sizeof(visited));    int i, j, d[105], f, tmp, ans=0;    visited[0]=1;    for(i=0; i<cnt; i++)    d[i]=a[0][i];    for(i=1; i<cnt; i++){        tmp=100000;        for(j=0; j<cnt; j++){            if(!visited[j]&&d[j]<tmp){                tmp=d[j];                f=j;            }        }        visited[f]=1;        ans+=tmp;        for(j=0; j<cnt; j++){            if(!visited[j]&&d[j]>a[f][j])            d[j]=a[f][j];        }    }    return ans;}void solve(){    for(int i=0; i<cnt; i++)        bfs(i);    printf("%d\n", prim());}int main(){    //freopen("1.txt", "r", stdin);    int T;    scanf("%d", &T);    getchar();    while(T--){        init();        solve();    }    return 0;}