【DFS】POJ 2044

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http://poj.org/problem?id=2044
#define N 366bool flag[8][8][8][8][10][N];//前四个是四个角的状态，第五个是云的左上角的位置，最后一个是第几天int day[N];int n;int d[9][2] = { {0,0},//九个位置                {-1,0},{-2,0},                {1,0},{2,0},                {0,-1},{0,-2},                {0,1},{0,2}              };//四个角7天内没雨，return false//该状态已存在，return false//是否有限制不能下雨bool chk(int x,int y,int num,int *a){    if(a[1]==7||a[2]==7||a[3]==7||a[4]==7)return false;    int pos = 3*x+y;    if(flag[a[1]][a[2]][a[3]][a[4]][pos][num] == true)return false;    int tmp = (1<<(15-4*x-y)) | (1<<(15-4*(x+1)-y)) | (1<<(15-4*x-(y+1))) | (1<<(15-4*(x+1)-(y+1)));    if((day[num]&tmp) != 0)return false;    flag[a[1]][a[2]][a[3]][a[4]][pos][num] = true;    return true;}bool dfs(int x,int y,int num,int *a){    if(num==n)return true;    if(chk(x,y,num,a) == false)return false;    int i,j,k;    for(i=0;i<9;i++){//(0,0)-->(2,2)        int xx = x+d[i][0];        int yy = y+d[i][1];        if(xx<0 || xx>2 || yy<0 || yy>2)continue;        int b[5];        b[1] = a[1]+1;        b[2] = a[2]+1;        b[3] = a[3]+1;        b[4] = a[4]+1;        if(xx==0 && yy==0)b[1] = 0;        if(xx==0 && yy==2)b[2] = 0;        if(xx==2 && yy==0)b[3] = 0;        if(xx==2 && yy==2)b[4] = 0;        if(dfs(xx,yy,num+1,b))return true;    }    return false;}int main(){    while(scanf("%d",&n) && n){        int i,j;        memset(day,0,sizeof(day));        memset(flag,false,sizeof(flag));        for(i=0;i<n;i++){            for(j=1;j<=16;j++){                int x;                scanf("%d",&x);                day[i] = (day[i]<<1) | x;            }        }        int a[5];//记录四个角没有下雨天数        a[1] = a[2] = a[3] = a[4] = 1;        if(dfs(1,1,0,a))printf("1\n");        else printf("0\n");    }    return 0;}