【BFS】ural 1033

BFS，不解釋。注意要從兩個入口開始找！

#include <vector>#include <list>#include <map>#include <set>#include <queue>#include <string>#include <deque>#include <stack>#include <algorithm>#include <iostream>#include <iomanip>#include <cstdio>#include <cmath>#include <cstdlib>#include <limits.h>#include <time.h>#include <string.h>using namespace std;int lowbit(int t){return t&(-t);}int countbit(int t){return (t==0)?0:(1+countbit(t&(t-1)));}int gcd(int a,int b){return (b==0)?a:gcd(b,a%b);}#define LL long long#define PI acos(-1.0)#define N  301#define MAX INT_MAX#define MIN INT_MIN#define eps 1e-8#define FRE freopen("a.txt","r",stdin)char c[40][40];int d[4][2]={{0,1},{0,-1},{1,0},{-1,0}};struct node{    int x,y;};int sum;int n;bool vis[40][40];void bfs(int x,int y){    queue<node> q;    node tmp;    tmp.x=x,tmp.y=y;    q.push(tmp);    while(!q.empty()){        tmp=q.front();        q.pop();        int xx,yy;        for(int i=0;i<4;i++){            xx=tmp.x+d[i][0];            yy=tmp.y+d[i][1];            if(xx<0 || yy<0 || xx>=n || yy>=n)            {sum++;continue;}            if(vis[xx][yy])continue;            if(c[xx][yy]=='#')            {sum++;continue;}            vis[xx][yy]=1;            node t;            t.x=xx,t.y=yy;            q.push(t);        }    }}int main(){    while(scanf("%d",&n)!=EOF){    int i,j;    for(i=0;i<n;i++)scanf("%s",c[i]);    sum=0;    memset(vis,0,sizeof(vis));    vis[0][0]=1;    bfs(0,0);    if(!vis[n-1][n-1]){        vis[n-1][n-1]=1;        bfs(n-1,n-1);    }//cout<<sum<<endl;    printf("%d\n",(sum-4)*9);    }    return 0;}