我爱崔老师系列之 新学的位运算枚举~ HDU4462 scaring the birds 杭州现场赛J题，枚举。

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=4462

当时比赛的时候读错题意了。。。很悲催的没有考虑n*n个稻草人的时候。。。。然后一直WA= =。。。悲剧啊。。。。

回来的时候崔老师教了一个枚举的办法。。。就是位运算。。之前做的一道DFS也可以用位运算来写（其实取1或者取0的dfs都可以用位运算写= =）~、

膜拜崔老师~

#include <iostream>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int map[55][55];
int hash[55][55],count,n;
using namespace std;
struct node
{
    int x,y,r;
}scare[15];
int top,q[100],ans,leap;
int judge()
{
    int i,j;
    for(i = 1;i <= n;i++)
    {
        for(j = 1;j <= n;j++)
        {
            if(!hash[i][j]&&map[i][j] == 0)
            return 0;
        }
    }
    return 1;
}
void reverse(int t)
{
    int i,j,x1,x2,y1,y2;
    x1 = scare[t].x-scare[t].r;
    x2 = scare[t].x+scare[t].r;
    y1 = scare[t].y-scare[t].r;
    y2 = scare[t].y+scare[t].r;
    if(x1 < 1)//防止数组越界
    x1 = 1;
    if(y1 < 1)
    y1 = 1;
    if(x2 > n)
    x2 = n;
    if(y2 > n)
    y2 = n;
    for(i = x1;i <= x2;i++)//在那个方格中找
    {
        for(j = y1;j <= y2;j++)
        {
            if(abs(i-scare[t].x)+abs(j-scare[t].y) <= scare[t].r && hash[i][j] != 1)
            map[i][j] = 1;
        }
    }
}
void recover(int t)
{
    int i,j,x1,x2,y1,y2;
    x1 = scare[t].x-scare[t].r;
    x2 = scare[t].x+scare[t].r;
    y1 = scare[t].y-scare[t].r;
    y2 = scare[t].y+scare[t].r;
    if(x1 < 1)//防止数组越界
    x1 = 1;
    if(y1 < 1)
    y1 = 1;
    if(x2 > n)
    x2 = n;
    if(y2 > n)
    y2 = n;
    for(i = x1;i <= x2;i++)
    {
        for(j = y1;j <= y2;j++)
        {
            if(abs(i-scare[t].x)+abs(j-scare[t].y) <= scare[t].r && hash[i][j] != 1)
            map[i][j] = 0;
        }
    }
}
int main()
{
    int m,i,j;
    while(scanf("%d",&n)&&n)
    {
        leap = 0;
        memset(map,0,sizeof(map));
        memset(hash,0,sizeof(hash));
        cin>>m;
        ans = 1000;
        for(i = 0;i < m;i++)
        {
            scanf("%d %d",&scare[i].x,&scare[i].y);
            hash[scare[i].x][scare[i].y] = 1;//把稻草人的地方标记一下，省的找了。。。稻草人本来就是空地不用考虑上不上色、
        }
        for(i = 0;i < m;i++)
        {
            cin>>scare[i].r;
        }

        if(n*n == m)
        {
            cout<<"0"<<endl;
            continue;
        }

        for(i = 0;i < (1<<m);i++)
        {
            count = top = 0;
            for(j = 0;j < m;j++)
            {
                if((1<<j)&i)//第J个在i情况中用到。
                {

                    count++;
                    reverse(j);
                    q[top++] = j;
                }
            }

            if(judge())
            {
                if(ans > count)
                ans = count;
                leap = 1;
            }
            while(top > -1)
            {
                recover(q[--top]);
            }
        }
        if(leap)
        cout<<ans<<endl;
        else
        puts("-1");


    }
    return 0;
}

#include<stdio.h>
#include<string.h>
char map[205][205];
struct node
{
    int x,y,step,f;//f存先驱，step是当前的步数。
}q[400005];

int way[400005];//用来最后存路径
int f,r,m,n,fa,leap;
int vis[205][205];
int to[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};//四个方向
void sort()//优先队列排序
{
    int i;
    struct node t;
    for(i = r;i > f;i--)
    {
        if(q[i].step < q[i-1].step)
        {
            t = q[i];
            q[i] =q[i-1];
            q[i-1] = t;
        }
        else
        break;
    }
}
void bfs()
{
    int i,j,nx,ny;
    memset(vis,0,sizeof(vis));
    f = r = 0;
    leap = 0;
    q[r].x = 0;
    q[r].y = 0;
    if(map[0][0] == 'X')//看看开头能不能走
    leap = 0;
    else
    {

    if(map[0][0] != '.'&& map[0][0] != 'X')//如果是数字的话开头是不能直接将STEP = 0 的。
    q[r].step = map[0][0]-'0';
    else
    q[r].step = 0;
    q[r].f = -1;
    vis[0][0] = 1;
    r++;
    while(f < r)
    {
        struct node now;
        fa = f;
        now = q[f++];
        for(i = 0;i < 4;i++)
        {
            nx = now.x+to[i][0];
            ny = now.y+to[i][1];

            if(nx >= 0 && nx < m && ny >= 0 && ny < n && map[nx][ny] != 'X' && !vis[nx][ny])
            {
                q[r].x = nx;
                q[r].y = ny;

                q[r].f = fa;
                if(map[nx][ny] == '.')
                q[r].step = now.step+1;
                else
                q[r].step = map[nx][ny]-'0'+now.step + 1;

                if(nx == m-1 && ny == n-1)
                {
                    leap = 1;
                    break;
                }
                 sort();//优先队列排序。。。这里一定不要加错位置、
                r++;
                vis[nx][ny] = 1;
            }
        }
        if(leap)
        break;
    }
    }
}
int main()
{


     
    int i,count,j,nt;
    while(~scanf("%d %d",&m,&n))
    {
        if(!(m||n))
        break;
        memset(map,0,sizeof(map));
        for(i = 0;i < m;i++)
        scanf("%s",map[i]);
        bfs();
        if(leap)
        {
            printf("It takes %d seconds to reach the target position, let me show you the way.\n",q[r].step);
            count = -1;
            while(1)
            {
                way[++count] = r;
                r = q[r].f;
                if(r == -1)
                break;
            }
            nt = 1;
            for(i = count;i > 0;i--)
            {
                printf("%ds:(%d,%d)->(%d,%d)\n",nt++,q[way[i]].x,q[way[i]].y,q[way[i-1]].x,q[way[i-1]].y);
                if(map[q[way[i-1]].x][q[way[i-1]].y] != '.' )
                {
                    int time;
                    time = map[q[way[i-1]].x][q[way[i-1]].y]-'0';
                    for(j = 0;j < time;j++)
                    {
                        printf("%ds:FIGHT AT (%d,%d)\n",nt++,q[way[i-1]].x,q[way[i-1]].y);
                    }
                }
            }

        }
        else
        puts("God please help our poor hero.");
        puts("FINISH");
    }
    return 0;
}