hdu5024-Wang Xifeng's Little Plot

此题一开始用暴力做，后来发现斜着走的时候其实暴力不太好写，于是改用搜索写了

#include <iostream>
#include <stdio.h>
#include <memory.h>
using namespace std;

char a[110][110]= {0};
int down[110][110]= {0};
int up[110][110]= {0};

int cnt[110][110][4]= {0};
int n;
int dx[4]= {-1,1,-1, 1};
int dy[4]= {-1,1, 1,-1};
int dfs(int curx,int cury,int num)
{
    if(curx<0 || cury<0 || curx>=n || cury>=n)
        return 0;
    int &ans=cnt[curx][cury][num];
    if(a[curx][cury]=='#')
        return ans=0;
    return ans=1+dfs(curx+dx[num],cury+dy[num],num);
}


int getMax()
{
    int ans=0;
    for(int i=0; i<n; i++)
        for(int j=0; j<n; j++)
        {
            ans=max(ans,down[i][j]+up[i][j]-1);
        }
    return ans;
}

int main()
{
    freopen("in.txt","r",stdin);

    while(scanf("%d",&n),n)
    {
        memset(down,0,sizeof down);
        memset(up,0,sizeof up);
        memset(cnt,0,sizeof cnt);
        for(int i=0; i<n; i++)
            scanf("%s",a[i]);

        for(int i=0; i<n; i++)
            for(int j=0; j<n; j++)
            {
                if(a[i][j]=='#')
                {
                    up[i][j]=down[i][j]=0;

                }
                else
                {
                    up[i][j]=down[i][j]=1;
                    if(i!=0)
                        up[i][j]=up[i-1][j]+1;
                    if(j!=0)
                        down[i][j]=down[i][j-1]+1;
                }
            }

        int ans=0;
        ans=max(ans,getMax());

        memset(down,0,sizeof down);
        memset(up,0,sizeof up);
        for(int i=n-1; i>=0; i--)
            for(int j=n-1; j>=0; j--)
            {
                if(a[i][j]=='#')
                {
                    up[i][j]=down[i][j]=0;
                }
                else
                {
                    up[i][j]=down[i][j]=1;
                    if(i!=n-1)
                        up[i][j]=up[i+1][j]+1;
                    if(j!=n-1)
                        down[i][j]=down[i][j+1]+1;
                }
            }

        ans=max(ans,getMax());

//---------------------------
        memset(down,0,sizeof down);
        memset(up,0,sizeof up);
        for(int i=0; i<n; i++)
            for(int j=n-1; j>=0; j--)
            {
                if(a[i][j]=='#')
                {
                    up[i][j]=down[i][j]=0;
                }
                else
                {
                    up[i][j]=down[i][j]=1;
                    if(i!=0)
                        up[i][j]=up[i-1][j]+1;
                    if(j!=n-1)
                        down[i][j]=down[i][j+1]+1;
                }
            }

        ans=max(ans,getMax());
//-------------------------------
        memset(down,0,sizeof down);
        memset(up,0,sizeof up);
        for(int i=n-1; i>=0; i--)
            for(int j=0; j<n; j++)
            {
                if(a[i][j]=='#')
                {
                    up[i][j]=down[i][j]=0;
                }
                else
                {
                    up[i][j]=down[i][j]=1;
                    if(i!=n-1)
                        up[i][j]=up[i+1][j]+1;
                    if(j!=0)
                        down[i][j]=down[i][j-1]+1;
                }
            }

        ans=max(ans,getMax());
//--------------------------------------------------

        for(int i=0; i<n; i++)
            for(int j=0; j<n; j++)
            {
                for(int num=0; num<4; num++)
                {
                    dfs(i,j,num);
                }
            }

        for(int i=0; i<n; i++)
            for(int j=0; j<n; j++)
            {
                ans=max(ans,cnt[i][j][0]+cnt[i][j][2]-1);
                ans=max(ans,cnt[i][j][0]+cnt[i][j][3]-1);
                ans=max(ans,cnt[i][j][1]+cnt[i][j][3]-1);
                ans=max(ans,cnt[i][j][1]+cnt[i][j][2]-1);
            }

        cout<<ans<<endl;
    }
    return 0;
}